Vitamin B6 (Pyridoxine HCl) is used to support or treat premenstrual syndrome (PMS), particularly PMS Type S, which is characterized by symptoms such as irritability, mood swings, and depression—thought to be related to serotonergic and neurotransmitter imbalances. The use of vitamin B6 for PMS has scientific support, though the quality and consistency of evidence is moderate at best.

Several randomized controlled trials (RCTs) and meta-analyses have assessed the efficacy of vitamin B6 for PMS. A notable meta-analysis (Wyatt et al., 1999, BMJ) concluded that vitamin B6 might be more effective than placebo in addressing overall PMS symptoms, particularly mood-related symptoms. Doses between 50-100 mg daily have been most commonly studied. The proposed mechanism is that vitamin B6 acts as a cofactor in the synthesis of neurotransmitters such as serotonin and dopamine, which may be dysregulated in PMS Type S.

However, the studies are heterogeneous in design, and many suffer from small sample sizes and potential bias. More recent reviews suggest that while there is evidence of benefit, it is not robust, and further high-quality research is needed to confirm efficacy and optimal dosing. Vitamin B6 is generally considered safe at recommended doses, but excessive intake can cause neuropathy.

In summary, there is some scientific evidence supporting the use of vitamin B6 for PMS Type S, especially for mood symptoms, but the strength of the evidence is moderate (rated 2 out of 5).