Arginine creatine

Other Names

arginine and creatine co-supplementationcreatine and L-arginineL-arginine and creatineL-arginine creatine combination

Synopsis

Arginine Creatine: A Comprehensive Reference Article

1. Overview and Conceptual Identity

The term arginine creatine encompasses two interrelated concepts in nutritional biochemistry and dietary supplementation. First, it refers to the well-established biosynthetic relationship between the amino acid L-arginine and creatine — arginine is an essential metabolic precursor from which creatine is synthesized endogenously in the human body. Second, it refers to the use of these two compounds together as a combined dietary supplement strategy, frequently seen in commercial sport-nutrition products that pair creatine monohydrate with arginine or its salt forms (most commonly L-arginine alpha-ketoglutarate, abbreviated AAKG). Understanding arginine creatine therefore requires mastery of both the underlying biochemistry linking these molecules and the independent as well as combined clinical evidence for each.

This article covers the chemical identity, biosynthesis, natural sources, historical and modern use, active mechanisms, body systems affected, clinical evidence by area of use, dosing, and safety profile of both compounds — with special attention to their biochemical interconnection and their combined use as a dietary supplement.

2. Chemical Identity and Nomenclature

2.1 Creatine

Creatine (α-methyl-guanidine-acetic acid) is one of the most popular dietary supplements, with a wide spectrum of potential applications. Creatine, a naturally occurring amino acid derivative, plays an important part in cellular energy metabolism. Creatine is a nonessential amino acid and is also a nitrogenous organic acid. Its full IUPAC name is 2-(1-methylguanidino)acetic acid, and it is sometimes written as N-(aminoiminomethyl)-N-methyl glycine. Creatine (N-(aminoiminomethyl)-N-methyl glycine) is a naturally occurring compound that when combined with phosphate provides energy for cellular metabolism.

2.2 L-Arginine

L-arginine, classified as a semi-essential amino acid, plays a central role in numerous physiological processes, most notably as a precursor for nitric oxide (NO) synthesis. Arginine is obtained from food and synthesized in the body. It is therefore referred to as a semi-essential amino acid. In healthy adults, food and synthesis in the body are sufficient to meet the necessary demands for this amino acid. Its full IUPAC name is (2S)-2-amino-5-(diaminomethylideneamino)pentanoic acid.

2.3 Arginine Alpha-Ketoglutarate (AAKG): The Common Combined Form

Arginine alpha-ketoglutarate is formed when two arginine molecules combine with one molecule of alpha-ketoglutarate. The combination of alpha-ketoglutarate and arginine improves the stability of arginine. This is supposed to improve its performance-enhancing abilities and its role in energy production. AAKG is a compound made from the amino acid L-arginine and alpha-ketoglutarate, a substance formed in the body's energy-generating process. AAKG is frequently sold in combination with creatine in multi-ingredient sport-nutrition products.

3. Natural Sources

3.1 Dietary Sources of Creatine

Creatine is an organic compound that is both synthesized endogenously and found exogenously in various food sources such as meats and fish. Creatine is found in fresh meat and fish in concentrations ranging from 3 to 10 grams per kg wet weight. A daily turnover of creatine is approximately 2.0 grams, and about half of this daily need for creatine (1.0 g/day) is obtained from the diet, while the rest is de novo synthesized inside the body. Creatine is notably absent in significant quantities in plant-based foods, making supplementation of particular relevance to vegetarians and vegans.

3.2 Dietary Sources of L-Arginine

Arginine can be independently manufactured by the human body, and does not need to be obtained directly through dietary intake. It is found in high concentrations in protein-rich foods including meats, seafood, nuts, seeds, beans, lentils, and whole grains. These demands include tissue repair, synthesis of proteins, and maintenance of immune function. During periods of rapid growth, physical stress, or injury, the supply of L-arginine may be insufficient to meet the body's needs.

3.3 AAKG as a Supplement-Only Form

Although the substances that comprise AAKG are present in many foods, the AAKG compound is found only in supplements.

4. Historical Discovery and Early Use

4.1 Discovery of Creatine

Creatine was first identified in 1832 when Michel Eugène Chevreul isolated the precipitate from the basified water-extract of skeletal muscle. He later named the crystallized precipitate after the Greek word for meat, κρέας (kreas). In 1847, the German scientist Justus von Liebig chemically identified creatine as methylguanidino-acetic acid, a relatively simple guanidino compound. Justus von Liebig supported his laboratory largely by producing and selling meat broth, the famous Liebig's meat extract or Fleischbrühe in German, which contained about 8% creatine.

A German scientist, Justus von Liebig, found that creatine was present in other meats as well, and went on to measure the creatine levels amongst different types of wildlife. Through his studies, he found that wild animals had approximately ten-times higher concentrations of creatine in their flesh than domesticated animals. Justus von Liebig suggested that creatine is important in producing muscular action in vertebrates.

In 1928, creatine was shown to exist in equilibrium with creatinine. Studies in the 1920s showed that consumption of large amounts of creatine did not result in its excretion. This result pointed to the ability of the body to store creatine, which in turn suggested its use as a dietary supplement.

Studies such as those by Chanutin, Walker, and Harris et al. in 1992 have all shown that supplemental creatine can augment natural human intramuscular creatine stores. The work of Harris and colleagues in the early 1990s is widely credited with launching the modern era of creatine supplementation, which subsequently received wide public attention in connection with the 1992 Barcelona Olympics.

4.2 Historical Use of Arginine

L-arginine was first isolated in 1886 by Ernst Schulze and Ernst Steiger from lupine seedlings. Its role as a precursor to nitric oxide was not established until research by Furchgott, Ignarro, and Murad — work that resulted in the 1998 Nobel Prize in Physiology or Medicine. There is no documented tradition of deliberate arginine supplementation in pre-modern medicine. The clinical and supplemental use of arginine developed entirely within the 20th century, initially in parenteral nutrition research and later in sports and cardiovascular medicine.

5. Biosynthetic Link: How Arginine Produces Creatine

The most fundamental connection between arginine and creatine is biochemical: creatine is synthesised de novo from the metabolism of the amino acids arginine, glycine and methionine. The enzymes involved in its synthesis are arginine:glycine amidinotransferase (AGAT) and guanidinoacetate N-methyltransferase (GAMT).

The two-step process proceeds as follows:

Step 1 (Kidney): Arginine glycine amidinotransferase (AGAT) is defined as an enzyme that catalyzes the first and rate-limiting step in creatine biosynthesis, facilitating the transfer of a guanidino group from L-arginine to glycine to produce guanidinoacetate (GAA) and ornithine. This is believed to be the regulated step of creatine biosynthesis.
Step 2 (Liver): The second enzyme in the pathway is guanidinoacetate methyltransferase (GAMT). This enzyme catalyzes the transfer of a methyl group from S-adenosylmethionine (SAM) to GAA to form S-adenosylhomocysteine (SAH) and creatine. There are high activities of AGAT in the kidneys and of GAMT in the livers of various species.

GAA is then methylated to creatine in the liver by the enzyme Guanidinoacetate N-methyltransferase (GAMT) using S-adenosylmethionine (SAM) as the methyl donor. The creatine is then transported through the bloodstream and taken up through sodium-dependent creatine transporters by cells that require creatine.

A fraction of the body's creatine and creatine phosphate spontaneously degrades to creatinine, which is excreted by the kidneys. In humans, this amounts to approximately 1–2 g/day and demands a comparable rate of de novo creatine synthesis.

Arginine is one of the three substrates to form creatine, which is a vital nutrient (deficiency induces mental retardation) and is also used to form agmatine, a signalling molecule in the body. When AGAT is deficient, severe creatine deficiency results: In 2000, The American Journal of Human Genetics reported two female siblings, aged 4 and 6 years, with intellectual disability and severe creatine deficiency in the brain. Arginine:glycine amidinotransferase (AGAT) catalyzes the first step of creatine synthesis, resulting in the formation of guanidinoacetate. In these two siblings with intellectual disability who had brain creatine deficiency that was reversible by means of oral creatine supplementation, AGAT deficiency was identified as a new genetic defect in creatine metabolism.

6. Key Active Compounds and Mechanisms of Action

6.1 Creatine and the Phosphocreatine Energy System

Creatine, when phosphorylated by creatine kinase with an adenosine triphosphate (ATP), forms a high-energy phosphocreatine (creatine phosphate), which is a significant cellular energy reserve, and an adenosine diphosphate (ADP). Phosphorylation by creatine kinase is reversible, thus phosphocreatine helps to supply energy to cells in the body by increasing the formation of ATP as needed.

The creatine kinase system has a dual role in intracellular energy metabolism: functioning as an energy buffer to restore depleted ATP levels at sites of high ATP hydrolysis, and transferring energy in the form of phosphocreatine from the mitochondria to other parts of the cell by a process involving intermediate energy carriers, several enzymatic reactions, and diffusion through various intracellular structures.

Approximately greater than 95% of the human body's total creatine is located in skeletal muscle and brain.

Mechanistically, creatine supplementation elevates skeletal muscle phosphocreatine (PCr) stores facilitating a greater capacity to rapidly resynthesize ATP and buffer hydrogen ion accumulation. When co-ingested with carbohydrates, creatine enhances glycogen resynthesis and content, an important fuel to support high-intensity aerobic exercise.

By increasing intracellular creatine content, oral creatine ingestion conceivably stimulates operation of the creatine kinase (CK)/phosphocreatine (PCr) system, which in turn facilitates muscle relaxation. Furthermore, evidence is accumulating to suggest that creatine supplementation can beneficially impact on muscle protein and glycogen synthesis. Thus, muscle hypertrophy and glycogen supercompensation are candidate factors to explain the ergogenic potential of creatine ingestion.

Found in all vertebrates, creatine kinase catalyzes the reversible reaction of creatine and ATP forming phosphocreatine and ADP. There are four major isozymes, two cytosolic and two mitochondrial, which form dimers and octamers, respectively.

6.2 L-Arginine and Nitric Oxide Synthesis

NO is produced enzymatically from L-arginine by nitric oxide synthases (NOS) and exerts far-reaching effects on cellular signalling and general health. As a critical regulator of homeostasis, NO contributes significantly to the maintenance of vascular tone and modulation of immune responses, highlighting its essential role in diverse biological systems.

Nitric oxide diffuses from endothelial cells into underlying smooth muscle, causing relaxation, which results in vasodilation. When this process is inhibited or inadequate the arteries cannot dilate as necessary, resulting in hypertonicity and reduced blood flow. Such endothelial dysfunction also causes increased platelet and monocyte adhesiveness and smooth muscle proliferation, processes thought to be at the genesis of atherosclerotic plaque formation. Since L-arginine is the body's only substrate for nitric oxide synthesis, adequate L-arginine must be present for proper nitric oxide production.

The reaction takes place in two steps: first, L-arginine is hydroxylated to form N-hydroxy-L-arginine, which is then further oxidised to form NO and citrulline.

6.3 Additional Mechanisms of Arginine

Arginine plays a significant role in healing, cell division, immune function, the elimination of ammonia from the body and the release of hormones. Arginine is an amino acid involved in two regulatory cycles (urea and nitric oxide) and can be converted into a few other bioactive molecules such as creatine or agmatine to regulate the body.

6.4 Rationale for Combined Arginine–Creatine Supplementation

Creatine (Cr) supplementation increases muscle mass, strength, and power. Arginine alpha-ketoglutarate (A-AKG) is a precursor for nitric oxide production and has the potential to improve blood flow and nutrient delivery (i.e., Cr) to muscles. The theoretical rationale for combining AAKG with creatine is therefore that AAKG-mediated vasodilation could enhance the muscular uptake and delivery of creatine itself. This mechanistic hypothesis, however, requires further direct testing.

7. Scientific Evidence by Area of Use

7.1 Athletic Performance and Muscle Strength (Creatine)

The evidence base for creatine in exercise performance is among the most robust of any dietary supplement. The increase of creatine stores can offer therapeutic benefits by preventing ATP depletion, stimulating protein synthesis or reducing protein degradation, and stabilizing biological membranes. Evidence from the exercise literature has shown athletes benefit from supplementation by increasing muscular force and power, reducing fatigue in repeated bout activities, and increasing muscle mass.

A 2025 systematic review and network meta-analysis incorporating data from 35 randomized controlled trials found that creatine supplementation demonstrated superior effects for muscle strength (SMD = 0.46, 95% CI: 0.29 to 0.63, SUCRA = 82.4%).

A systematic review and meta-analysis of creatine supplementation in soccer players (9 studies) found that creatine supplementation did not present beneficial effects on aerobic performance tests (SMD, −0.05; 95% CI, −0.37 to 0.28; p = 0.78) and phosphagen metabolism performance tests. However, creatine supplementation showed beneficial effects on anaerobic performance tests (SMD, 1.23; 95% CI, 0.55–1.91; p < 0.001). Concretely, creatine demonstrated a large and significant effect on Wingate test performance (SMD, 2.26; 95% CI, 1.40–3.11; p < 0.001).

Evidence strength: Strong. There are multiple systematic reviews and meta-analyses from well-controlled RCTs demonstrating that creatine augments high-intensity anaerobic performance and muscle strength. Evidence for endurance or aerobic benefits is less consistent.

7.2 Combined Creatine + AAKG in Athletic Performance

A 10-day double-blind randomized controlled trial (n=35 men, approximately 23 years old) compared creatine plus AAKG, creatine alone, and placebo: Body composition, muscle endurance (bench press), and peak and average power (Wingate tests) were measured. Bench-press repetitions over 3 sets increased with Cr + A-AKG (30.9 ± 6.6 to 34.9 ± 8.7 reps; p < .01) and Cr alone (27.6 ± 5.9 to 31.0 ± 7.6 reps; p < .01), with no difference between groups. Peak power significantly increased in Cr + A-AKG (741 ± 112 to 794 ± 92 W; p < .01), with no changes in Cr alone or placebo. These results suggest that Cr alone and in combination with A-AKG improves upper body muscle endurance, and Cr + A-AKG supplementation improves peak power output on repeated Wingate tests.

An 8-week double-blind placebo-controlled trial of AAKG alone (4 g three times daily, i.e., 12 g daily, n=20 resistance-trained men aged 30–50 years) found: No significant differences were observed between groups in body composition, total body water, isokinetic quadriceps muscle endurance, or aerobic capacity. AAKG supplementation appeared to be safe and well tolerated, and positively influenced 1RM bench press and Wingate peak power performance.

In contrast, a separate double-blind crossover study (n=16 men; 3,000 mg AAKG vs. placebo, 45 minutes pre-exercise) found: Acute AAKG supplementation provides no ergogenic benefit on 1RM or total load volume as measured by the standard barbell bench press and leg press, regardless of the subjects' training status.

Evidence strength: Mixed and preliminary. Some evidence supports modest ergogenic benefits of AAKG when combined with creatine or when used chronically, but acute single-dose studies show no benefit. Small sample sizes and short durations limit conclusions.

7.3 AAKG and Nitric Oxide / Blood Flow

Arginine alpha-ketoglutarate combined had no effects on heart rate, blood pressure, blood flow, or nitric oxide levels in some trials. While L-arginine by itself is known to increase nitric oxide production, no research has been done to show that AAKG does the same.

Evidence strength: Weak. The evidence that AAKG specifically increases measurable circulating nitric oxide levels or produces significant vasodilation in exercising humans is limited and inconsistent.

7.4 L-Arginine and Blood Pressure / Cardiovascular Health

A 2022 systematic review and dose-response meta-analysis of 22 RCTs (30 effect sizes) found: The pooled analysis demonstrated significant decreases in systolic blood pressure (WMD = -6.40 mmHg; 95% CI: -8.74, -4.05; P < 0.001) and diastolic blood pressure (WMD = -2.64 mmHg; 95% CI: -3.94, -1.40; P < 0.001) after L-arginine supplementation.

Although the findings of this meta-analysis support the beneficial effects of L-arginine administration on hemodynamic parameters, it should be emphasized that comorbidities of the patients, baseline blood pressure, dosage of L-arginine supplementation, and the duration of therapy differed considerably between the trials. There are conflicting results regarding the outcome of oral L-arginine supplementation in clinical studies, which can be due to the heterogeneous patient population and the treatment protocol used. The maximal effective dose of L-arginine supplementation with only minor gastrointestinal side effects seems to be 21 g daily, divided into three doses.

Evidence strength: Moderate. A meta-analysis supports statistically significant blood pressure reductions, but substantial heterogeneity across trials, varying populations, and dose inconsistencies make generalization difficult. L-arginine is not currently a first-line recommendation for hypertension management.

7.5 Creatine in Aging, Sarcopenia, and Functional Capacity

Accumulating research shows that creatine monohydrate supplementation (CrM), primarily when combined with exercise training, is safe and has beneficial effects on measures of whole-body lean body mass, regional muscle size, muscle strength, bone area and thickness, functional ability, glucose kinetics, cognition and memory. CrM has multiple benefits in older adults and may have application for treating age-related sarcopenia, osteoporosis, frailty, and those with metabolic and neuromuscular disorders.

In summary, there is accumulating evidence that CrM (≥3 grams/day) combined with resistance training is a viable intervention for improving strength, whole-body lean mass, regional muscle size and density, and select measures of functional ability in older adults.

Creatine supplementation, particularly when combined with resistance training, significantly improves muscle strength, lean body mass, and functional capacity in older adults. Cognitive outcomes show modest improvements in memory, processing speed, and executive function, especially in individuals with lower baseline creatine levels. Mechanistically, creatine supports energy metabolism, mitochondrial stability, and antioxidant defenses, while exercise promotes neuroplasticity through myokines, collectively reinforcing the muscle–brain axis.

Evidence strength: Moderate to strong. Multiple RCTs and narrative reviews support creatine's benefits in aging populations, particularly in combination with resistance training. Standalone effects without exercise are less well established.

7.6 Creatine and Cognitive Function

Two studies conducted double-blinded interventions, one of which was a randomized controlled trial; in both intervention studies, participants were supplemented with creatine monohydrate. The current limited evidence suggests that creatine may be associated with benefits for cognition in generally healthy older adults. However, high-quality clinical trials are warranted to further validate this relationship.

The two intervention studies included in the systematic review reported conflicting results. The methods used within these studies varied widely, with one being an RCT of 24 weeks and the other being an intervention without explicit mention of randomization and only seven days of creatine supplementation. Similarly, the cognitive tasks and outcomes assessed in each study differed, making it difficult to compare the study results. As such, there is a need for high-quality and long-term clinical trials with consistent protocols and assessments.

A study including 128 young adult women found that 20 g/day of creatine for five days improved memory in vegetarians, but not in omnivores, while enhancing performance on a choice reaction-time task in both groups.

Evidence strength: Preliminary. Evidence for cognitive benefits of creatine is emerging but inconsistent; vegetarians and those with low baseline brain creatine may benefit more. High-quality, large-scale RCTs are lacking.

7.7 Creatine in Neurological and Clinical Disease

Benefits have been applied to disease models of Huntington's, Parkinson's, Duchenne muscular dystrophy, and applied clinically in patients with gyrate atrophy, various neuromuscular disorders, McArdle's disease, and congestive heart failure.

Oral administration of creatine can increase muscle creatine content, with consistent evidence showing that creatine supplementation can benefit performance in certain sports and improve some clinical symptoms, for instance in rheumatic diseases, metabolic disturbances, myopathies, neurodegenerative diseases, chronic obstructive pulmonary disease, and congestive heart failure.

Evidence strength: Variable by condition. Evidence is more compelling for some conditions (neuromuscular disorders, gyrate atrophy) and remains exploratory for others (Huntington's, Parkinson's). Individual disease-specific trials show heterogeneous results and many are small or Phase I/II in scale.

7.8 Arginine and Immune/Wound Healing Function

During periods of rapid growth, physical stress, or injury, the supply of L-arginine may be insufficient to meet the body's needs. During this time, L-arginine taken as a dietary supplement may help maintain muscle mass and improve bodily function. Arginine is used clinically in parenteral and enteral nutrition formulas for critically ill and post-surgical patients, often in combination with other immunonutrients, based on its role in immune cell function and wound healing. This is a distinct area of use from supplemental ergogenics, and the evidence supporting it comes largely from clinical nutrition rather than dietary supplement research.

Evidence strength: Moderate in clinical nutrition settings; limited by study heterogeneity in healthy populations.

8. Body Systems and Health Areas

Musculoskeletal system: Creatine is strongly associated with skeletal muscle energy metabolism, hypertrophy, strength, and power; both arginine and creatine support muscle protein synthesis and recovery.
Cardiovascular system: Arginine is a primary determinant of vascular NO production, endothelial function, and blood pressure regulation. Cardiovascular scientists have long regarded creatine as an essential metabolite in the network of energy transfer. The evidence for creatine and phosphocreatine as intermediaries of energy transfer is compelling and supported by a large body of literature.
Nervous system / Brain: Creatine, a molecule important in transient energy storage from high-energy phosphates of ATP, is a third molecule synthesized from arginine. The creatine synthetic pathway is important in tissues with fluctuating energy needs such as muscle but is important as a rapid source of ATP-derived energy in many other tissues, including the brain, retina, and spermatozoa.
Immune system: Arginine modulates T-lymphocyte activity and macrophage function via NO-dependent and NO-independent pathways.
Renal and hepatic systems: The kidney is the principal site of AGAT activity and creatine precursor production; the liver is the principal site of GAMT activity and creatine completion. Both organs are involved in the creatine-arginine metabolic axis. The liver has high GAMT activity and the kidney has high AGAT activity.
Bone: CrM during resistance training programs has some potential to improve bone health and prevent falls.
Endocrine system: Arginine is used in the dietary supplement industry to boost human growth hormone (HGH) production, increase vasodilation, enhance blood circulation, increase oxygen flow to the muscles, and boost nitric oxide production.

9. Common Forms and Preparations

Various supplemental arginine forms are available in the consumer marketplace. The most commonly encountered forms for each compound, as documented in clinical research and the supplement literature, are as follows:

Creatine monohydrate: The most extensively studied and widely used form; the benchmark against which other creatine forms are measured.
Creatine hydrochloride (HCl): A newer, more soluble form increasingly studied in clinical contexts.
Creatine ethyl ester, creatine pyruvate, and other salts: Available commercially; substantially less studied than creatine monohydrate. The safety profile of alternative commercialized forms of creatine other than creatine monohydrate cannot be fully established because these novel formulations have been much less studied.
L-Arginine (free base): Standard oral form; used in most cardiovascular and immunology clinical trials.
Arginine alpha-ketoglutarate (AAKG): Arginine in combination with alpha-ketoglutarate (as arginine alpha-ketoglutarate [AAKG]) has been mainly manufactured and marketed to athletes for its performance-enhancing potential.
Multi-ingredient sports formulas: Arginine and/or AAKG are commonly sold in combination with creatine, glutamine, taurine, branched-chain amino acids, and medium-chain triglycerides as pre-workout or muscle-building supplements.

Both compounds are available in powders (most common for creatine), capsules, tablets, and ready-to-drink forms.

10. Dosages Reported in Clinical Research

The following dosages are presented only as documented in published research sources:

Creatine monohydrate — Loading: Protocols typically involve a loading phase, e.g., 20 g/day for 5 days, followed by a maintenance phase. In one RCT, creatine supplementation groups received 4 × 5 g/day for five days, followed by 5 g/day for 24 weeks.
Creatine monohydrate — Maintenance in older adults: There is accumulating evidence that CrM at ≥3 grams/day combined with resistance training is a viable intervention.
Creatine — Long-term trials: One large long-term clinical trial on Parkinson's patients provided 10 g/day of creatine monohydrate for up to 8 years.
Creatine + AAKG — combined supplement trial: Thirty-five men were randomized to Cr + A-AKG (0.1 g/kg/day Cr + 0.075 g/kg/day A-AKG) or Cr (0.1 g/kg/day) or placebo for 10 days.
AAKG — 8-week trial: 35 resistance-trained adult men (30–50 years old) were randomly assigned to ingest 4 g of AAKG three times a day (i.e., 12 g daily).
AAKG — Acute crossover study: Eight resistance trained and eight untrained healthy males ingested either 3,000 mg of AAKG or a placebo 45 minutes prior to a resistance exercise protocol in a randomized, double-blind crossover design.
L-Arginine — Vasodilation dosing: Considerable amounts of arginine are required to produce a significant vasodilating effect, with common doses ranging from eight to twenty-four grams per day.
L-Arginine — Maximum tolerated dose: The maximal effective dose of L-arginine supplementation with only minor gastrointestinal side effects seems to be 21 g, daily divided into three doses.
Daily body requirement for creatine: Creatine is a naturally occurring compound that is a primary constituent of phosphocreatine that provides cellular energy. The daily need for creatine is about 2–4 g/day.

11. Safety Considerations and Drug/Nutrient Interactions

11.1 Overall Safety Profile of Creatine

The evidence suggests that creatine monohydrate supplementation is generally safe when used appropriately, with further research needed to understand its impact on specific populations. Most controlled studies of creatine report an absence of side effects or report no differences in the incidence of side effects between creatine and placebo. Mihic and colleagues demonstrated that creatine loading increases fat-free mass, but does not affect blood pressure or plasma creatinine in adult men and women.

No significant differences were observed in the number of studies reporting 33 side effects between the placebo and creatine-supplemented groups, with the difference in prevalence typically ±0.4%. This includes the number of studies reporting vertigo, hypertension, headache, dizziness, lightheadedness, nausea, diarrhea, impaired concentration, sleep disturbances, poor appetite, fatigue, excessive sweating, edema, palpitations, thromboembolic events, kidney-related issues, and elevated liver enzymes.

11.2 Renal Safety

Despite a few case reports and animal studies suggesting that creatine may impair kidney function, clinical trials with controlled designs do not support this claim. Creatine supplementation may increase serum creatinine concentration for some individuals, but it does not necessarily indicate kidney dysfunction, as creatine is spontaneously converted into creatinine. Based on studies assessing kidney function using reliable methods, creatine supplements have been shown to be safe for human consumption. Further studies with people who have pre-existing kidney disease remain necessary.

Concerns about high-dose creatine's association with renal toxicity are based exclusively on two published case reports; in one of the cases the patient had a documented pre-existing kidney condition. Literature reviews and expert consensus panels have concluded there is no evidence supporting an association between creatine and renal disease.

Poortmans conducted studies of the effect of creatine supplementation on renal function, showing that short-term supplementation does not alter glomerular filtration rate, and that chronic supplementation of up to five years' duration did not impair renal function in healthy athletes.

There is a scant amount of long-term studies (greater than 16 weeks) evaluating the impact of creatine supplementation on kidney health. There is also very limited evidence that creatine supplementation is safe for those with pre-existing kidney diseases, a very important limitation in the literature. Considering that a significant part of creatine consumers use many other substances, the impact of "polypharmacy" as a burden to kidney function cannot be disregarded.

11.3 Gastrointestinal Effects

Gastrointestinal distress is reported in some individuals, particularly at high doses, but such effects are dose-dependent and not universally experienced.

11.4 Dehydration and Cramp Claims

Claims that creatine leads to dehydration or muscle cramps during exercise are largely unsupported by controlled studies, which demonstrate no significant effects on hydration or thermoregulation; in fact, creatine may reduce the incidence of muscle cramps and assist in maintaining thermoregulatory balance.

11.5 Safety of AAKG

In an eight-week double-blind trial, weight lifters taking 4 grams of AAKG three times a day reported no significant side effects, showed no changes in blood pressure or heart rate, and had no abnormalities on standard blood tests for general health. These athletes also reported no undesirable changes in general health, mental health, libido, sleep quality, or other quality of life measures.

No clear interactions between AAKG and other nutrients have been established.

11.6 Arginine and Herpes Simplex Virus

Some physicians note a theoretical concern that supplemental arginine may stimulate the replication of herpes simplex virus (types 1 and 2), given the known role of arginine in viral metabolism, and this concern has been referenced in the clinical literature. Some doctors believe that people with herpes (either cold sores or genital herpes) should not take arginine supplements, because of the possibility that arginine might stimulate replication of the virus. The evidence for this interaction is primarily theoretical and based on in-vitro data rather than robust human trials.

11.7 Populations Requiring Caution

In terms of kidney health, studies consistently show no adverse effects on renal function in healthy individuals, though caution is advised for those with pre-existing kidney conditions and pregnant women, as evidence is lacking for these populations.

11.8 Confounding Variable: Creatinine Elevation

Creatine supplementation may increase serum creatinine concentration for some individuals, but it does not necessarily indicate kidney dysfunction, as creatine is spontaneously converted into creatinine. This has historically led to misdiagnosis of kidney impairment in creatine-supplementing individuals, an issue recognized in the clinical literature.

12. Evidence Gaps and Research Limitations

Several important evidence gaps remain across the arginine creatine landscape:

The direct ergogenic or pharmacokinetic synergy of the arginine–creatine combination (as opposed to creatine alone) has been tested in only a small number of short-duration, small-sample trials.
Creatine supplementation is an effective ergogenic aid to augment resistance training and improve intense, short-duration, intermittent performance. The effects on endurance performance are less known.
High-quality clinical trials are warranted to further validate the relationship between creatine and cognition. Future research should investigate creatine supplementation in older clinical populations with notable cognitive deficits, objectively measure creatine concentrations, and consider additional factors that may influence creatine levels.
The combination of creatine supplementation and structured exercise appears to be a safe and promising strategy to counteract age-related declines in both physical and cognitive functions. However, further large-scale studies are required to establish long-term benefits and optimize dosing protocols.
The optimal timing, form, and dose of combined arginine–creatine supplementation, particularly in clinical populations, remains undefined.

References

Health Conditions

Health conditions that Arginine creatine may help support.

No conditions available.

Body Systems

Body systems that Arginine creatine may help support.

No body systems available.