Vitamin B2
Also known as: Riboflavin
What Does Vitamin B2 Measure?
Vitamin B2, also known as riboflavin, is a water-soluble B vitamin that plays a critical role in energy production and cellular function. A blood test measuring riboflavin assesses the concentration of this vitamin in the plasma or red blood cells, reflecting both recent dietary intake and overall nutritional status. Riboflavin is essential for the formation of two key coenzymes — flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) — which are involved in hundreds of metabolic reactions throughout the body.
Why Does Vitamin B2 Matter?
Riboflavin is vital for converting carbohydrates, fats, and proteins from food into usable energy (ATP). It supports the function of the mitochondria, the powerhouse of cells, and plays a significant role in the metabolism of other B vitamins, including B6, B9 (folate), and B12. Beyond energy metabolism, riboflavin acts as an antioxidant, supports healthy skin and mucous membranes, promotes proper eye function, and is critical during periods of growth, pregnancy, and breastfeeding. Deficiency can lead to a condition called ariboflavinosis, which presents with symptoms such as cracked lips, sore throat, skin rashes, and anemia.
Normal Ranges
Males
0.137–0.370 mg/L (or 137–370 nmol/L) in plasma
Females
0.137–0.370 mg/L (or 137–370 nmol/L) in plasma
Children
Varies by age; generally 0.1–0.35 mg/L; consult pediatric reference ranges
Causes of High Levels
- Excessive supplementation or intake of high-dose riboflavin supplements
- High dietary intake of riboflavin-rich foods combined with supplementation
- Liver disease, which can impair riboflavin metabolism and cause accumulation
- Certain medications that interfere with riboflavin clearance
- Laboratory error or sample contamination affecting test results
Causes of Low Levels
- Inadequate dietary intake, particularly in populations avoiding dairy and meat
- Malabsorption disorders such as celiac disease, Crohn's disease, or short bowel syndrome
- Chronic alcoholism, which impairs riboflavin absorption and increases its excretion
- Hypothyroidism, as thyroid hormones regulate riboflavin conversion to active forms
How to Improve Your Vitamin B2
Diet
- Consume beef liver and organ meats, which are among the richest dietary sources of riboflavin (liver provides ~2.9 mg per 3 oz serving)
- Include dairy products such as milk, yogurt, and cheese daily, as they are excellent riboflavin sources (1 cup of milk provides ~0.45 mg)
- Eat eggs regularly, especially the egg white, which is a good source of riboflavin (~0.23 mg per large egg)
- Incorporate lean meats, poultry, and fatty fish like salmon and trout into your weekly meals
- Add fortified cereals and whole grains to your diet, as many are enriched with riboflavin to meet daily requirements
- Include leafy green vegetables such as spinach, asparagus, and broccoli, which provide moderate amounts of riboflavin
Supplements
- Riboflavin supplements are commonly available in doses of 10–400 mg; the RDA is 1.1–1.3 mg/day for adults
- For deficiency correction, doses of 5–30 mg/day in divided doses are typically recommended under medical supervision
- Riboflavin 400 mg/day has been studied and used therapeutically for migraine prevention in adults
- B-complex vitamins containing riboflavin (usually 1.7–100 mg) can help maintain adequate levels alongside other B vitamins
Related Biomarkers
Frequently Asked Questions
What are the symptoms of riboflavin (Vitamin B2) deficiency?
Riboflavin deficiency, known as ariboflavinosis, typically presents with cracked or sore lips (cheilosis), cracks at the corners of the mouth (angular stomatitis), a sore and red tongue (glossitis), skin rashes particularly around the nose and genitals, sensitivity to light (photophobia), and bloodshot or itchy eyes. In more severe or prolonged deficiency, anemia and nerve damage may also occur. These symptoms can overlap with deficiencies of other B vitamins, so laboratory testing is important for accurate diagnosis.
Can too much Vitamin B2 be harmful or toxic?
Riboflavin toxicity is considered extremely rare because it is a water-soluble vitamin and excess amounts are efficiently excreted in the urine, which may turn bright yellow or fluorescent — a harmless side effect. The body has a limited capacity to absorb large doses at once, further reducing the risk of accumulation. No tolerable upper intake level (UL) has been established for riboflavin by most health authorities due to its low toxicity profile. However, very high supplemental doses should only be taken under medical supervision.
Why is Vitamin B2 important during pregnancy?
Riboflavin is particularly important during pregnancy because it supports rapid cell growth, energy production, and the healthy development of the fetus. It plays a role in the metabolism of folate and other B vitamins that are critical for preventing neural tube defects. Pregnant women have increased riboflavin requirements (approximately 1.4 mg/day), and deficiency has been associated with preeclampsia, poor fetal growth, and complications during delivery. Prenatal vitamins typically include riboflavin to help meet these elevated demands.