Vitamin B2 (Riboflavin)
Also known as: Riboflavin, Vitamin G
Riboflavin is an essential component of the coenzymes FAD and FMN, which are critical for various cellular oxidative and reductive reactions. It participates in mitochondrial energy production, acts as an antioxidant by supporting glutathione reductase, and is involved in the metabolism of other B vitamins, including folate and vitamin B6. Deficiency can lead to ariboflavinosis, characterized by oral-mucosal lesions, skin issues, and ocular symptoms.
Last reviewed: 2026-04-22 · 3 indexed studies
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Overview
Vitamin B2, also known as riboflavin, is a water-soluble vitamin essential for numerous metabolic processes. It plays a crucial role in cellular growth, energy production, and the metabolism of fats, drugs, and steroids. Riboflavin is a precursor to flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), two coenzymes vital for enzyme functions including those involved in the electron transport chain.
Mechanism & Function
Riboflavin · C₁₇H₂₀N₄O₆ — source: PubChem CID 493570
Bright yellow-orange crystalline B-vitamin. Tints urine fluorescent yellow.
- Capsule
- Tablet
- Powder
Capsule is generally preferred for bioavailability or efficacy.
Mechanism of Action
Riboflavin functions primarily as a precursor to the coenzymes flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN). FAD and FMN are prosthetic groups for flavoproteins, which catalyze various oxidative-reductive reactions. They are involved in the electron transport chain for ATP production, fatty acid oxidation, and the metabolism of carbohydrates and proteins. Riboflavin also supports antioxidant defense systems through its role in glutathione reductase activity.
Physiological Role
Riboflavin is crucial for energy metabolism, acting as a coenzyme in the form of FAD and FMN for numerous oxidoreductases. These enzymes are involved in the citric acid cycle, fatty acid beta-oxidation, and the electron transport chain. It also plays a key role in the metabolism of other vitamins (folate, B6, niacin), and supports antioxidant function by being a cofactor for glutathione reductase, an enzyme that regenerates reduced glutathione.
Primary Pathways
Performance / Health Relevance
Riboflavin's role in energy metabolism makes it vital for athletic performance, as it directly supports ATP production. Adequate intake ensures efficient utilization of carbohydrates, fats, and proteins for fuel. Its antioxidant properties may help mitigate exercise-induced oxidative stress. Deficiencies can impair energy production, leading to fatigue and reduced physical capacity.
Evidence Review
Practical Use & Dosage
- Minimum Effective Dose
- 2-3 mg/day for general health; 50-400 mg/day for specific conditions like migraine prophylaxis
- Optimal Range
- 2-10 mg/day
- Upper / Caution Level
- No established Upper Limit (UL) due to low toxicity; doses up to 400 mg/day have been used safely under medical supervision.
- Timing
- Can be taken at any time of day, preferably with a meal to enhance absorption.
- Best Format
- Oral supplements (tablets, capsules).
- Bioavailability
- Absorption occurs primarily in the small intestine via a saturable transport system. Bioavailability decreases with increasing single doses.
- Absorption Considerations
- Alcohol interferes with riboflavin absorption. Enhanced absorption with food.
Safety & Interactions
Side Effects
- •Bright yellow urine (harmless)
Contraindications
- Known hypersensitivity to riboflavin
- Caution in patients with biliary obstruction (reduced absorption)
Drug Interactions
- •Anticholinergic drugs (can inhibit absorption)
- •Tricyclic antidepressants (may inhibit absorption)
- •Phenothiazines (may increase riboflavin excretion)
- •Probenecid (may decrease absorption)
Who Should Avoid
- •Individuals with known allergies to riboflavin.
Monitoring
Monitoring is generally not required for typical supplemental doses. High doses may warrant monitoring for specific therapeutic uses.
Frequently Asked Questions
Auto-generated from indexed evidence — dosage, safety, interactions, and more.
When is Vitamin B2 (Riboflavin) typically used or indicated?
Vitamin B2 (Riboflavin) is most commonly used for: Energy production, Antioxidant support, Migraine prevention. Riboflavin is crucial for energy metabolism, acting as a coenzyme in the form of FAD and FMN for numerous oxidoreductases. These enzymes are involved in the citric acid cycle, fatty acid beta-oxidation, and the electron transport chain. It also plays a key role in the metabolism of other vitamins (folate, B6, niacin), and supports antioxidant function by being a cofactor for glutathione reductase, an enzyme that regenerates reduced glutathione.
How does Vitamin B2 (Riboflavin) work?
Riboflavin functions primarily as a precursor to the coenzymes flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN). FAD and FMN are prosthetic groups for flavoproteins, which catalyze various oxidative-reductive reactions. They are involved in the electron transport chain for ATP production, fatty acid oxidation, and the metabolism of carbohydrates and proteins. Riboflavin also supports antioxidant defense systems through its role in glutathione reductase activity.
What is the recommended dose of Vitamin B2 (Riboflavin)?
The optimal range is 2-10 mg/day. with a minimum effective dose of 2-3 mg/day for general health; 50-400 mg/day for specific conditions like migraine prophylaxis. Best taken: Can be taken at any time of day, preferably with a meal to enhance absorption.. Upper / caution level: No established Upper Limit (UL) due to low toxicity; doses up to 400 mg/day have been used safely under medical supervision..
What are the side effects of Vitamin B2 (Riboflavin)?
Reported side effects include: Bright yellow urine (harmless). Monitoring: Monitoring is generally not required for typical supplemental doses. High doses may warrant monitoring for specific therapeutic uses.
Does Vitamin B2 (Riboflavin) interact with medications?
Known or theoretical interactions: Anticholinergic drugs (can inhibit absorption); Tricyclic antidepressants (may inhibit absorption); Phenothiazines (may increase riboflavin excretion); and Probenecid (may decrease absorption). Always check with a clinician before combining with prescription medication.
Who should avoid Vitamin B2 (Riboflavin)?
Vitamin B2 (Riboflavin) is generally not recommended for: Individuals with known allergies to riboflavin.; Known hypersensitivity to riboflavin; and Caution in patients with biliary obstruction (reduced absorption).
How strong is the evidence for Vitamin B2 (Riboflavin)?
Evidence level: Moderate (overall score 65/100), based on 3 indexed studies on SuppIndex.
Research & References (3)
Riboflavin (vitamin B2) and migraine prophylaxis: a systematic review and meta-analysis.
This meta-analysis investigated the efficacy of riboflavin for migraine prophylaxis. It concluded that riboflavin supplementation significantly reduced attack frequency and duration in adult migraineurs, with fewer adverse events compared to placebo.
Effect of riboflavin on erythrocyte glutathione reductase activity and homocysteine levels in patients after stroke.
This randomized controlled trial examined the effect of riboflavin supplementation on erythrocyte glutathione reductase (EGR) activity and homocysteine levels in stroke patients. Riboflavin significantly improved EGR activity and reduced homocysteine levels, suggesting a role in cardiovascular health.
Riboflavin in the treatment of inherited metabolic disorders.
This systematic review discusses the therapeutic use of riboflavin in various inherited metabolic disorders, particularly those involving flavin-dependent enzymes. It highlights the importance of pharmacological doses of riboflavin in correcting enzymatic defects and improving clinical outcomes in specific populations.
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Research Overview
Moderate EvidenceCite this ingredient
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Stable URL
https://thesuppindex.com/ingredients/vitamin-b2-riboflavin
SuppIndex. (2026). Vitamin B2 (Riboflavin): Evidence summary, dosage and clinical studies. Retrieved October 23, 2026, from https://thesuppindex.com/ingredients/vitamin-b2-riboflavin
Based on 3 indexed studies · Evidence level: Moderate.
Goal Ratings
Stack Compatibility
Generally very compatible with other vitamins and minerals. Often included in B-complex formulations.