Vitamin B12 is commonly used to support convalescence, which refers to the period of recovery following illness or medical treatment. The justification for its use is grounded in scientific evidence, particularly in populations at risk of Vitamin B12 deficiency, such as the elderly, those with malabsorption syndromes, gastrointestinal surgeries, or those recovering from illnesses that impair nutritional intake or absorption. Vitamin B12 is essential for DNA synthesis, red blood cell formation, and neurological function. Deficiency can lead to megaloblastic anemia, fatigue, and neurological symptoms that can complicate recovery during convalescence.

Clinical studies have demonstrated that correcting a B12 deficiency in convalescent patients improves hematological and neurological parameters, and may enhance overall recovery. For example, supplementation is recommended in individuals recovering from gastrointestinal surgery or chronic illnesses that impede nutrient absorption. However, in otherwise healthy individuals without evidence of deficiency, the benefits of supplemental B12 during convalescence are less clear. There is limited direct evidence that B12 supplementation accelerates recovery in the absence of deficiency, but it is often included in multivitamin preparations for patients with poor oral intake during the recovery period.

In summary, Vitamin B12 has a scientific rationale for use during convalescence, particularly in those at risk of deficiency, but routine supplementation in all convalescent patients is not universally supported by high-level evidence.