What Happens When Vitamin B2 Is Low?

December 22, 2025 •

4 min read

Riboflavin deficiency, also known as ariboflavinosis, is a rare occurrence in developed countries like the United States due to fortified foods, yet many people worldwide still face inadequate intake. This essential vitamin, also known as B2, is critical for energy production and cellular function.

Quick Summary

A deficiency in vitamin B2 (riboflavin) can cause various symptoms, including cracked lips, a sore tongue, skin rashes, and eye issues. It often stems from insufficient dietary intake or malabsorption, impacting metabolism and overall health.

Key Points

Oral Symptoms: A clear sign of low vitamin B2 is often cracking and fissures of the lips (cheilosis) and sores at the corners of the mouth (angular stomatitis).
Energy and Metabolism: Since vitamin B2 is critical for energy production, a deficiency can lead to feelings of weakness and persistent fatigue.
Risk Factors: Pregnant or lactating women, vegans, and people with chronic alcohol use or malabsorption disorders are at a higher risk of deficiency.
Diagnosis: A doctor can diagnose riboflavin deficiency based on clinical signs, medical history, and confirmation via supplementation response or lab tests.
Treatment: Correcting a riboflavin deficiency involves increasing dietary intake of rich foods like dairy and meat or taking supplements under medical supervision.
Genetic Link: In rare cases, a genetic mutation affecting riboflavin transporters can cause a severe neurological disorder known as RTD.

What is Riboflavin?

Riboflavin, or vitamin B2, is a water-soluble vitamin that plays a vital role in human metabolism and health. As an essential component of two major coenzymes, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), riboflavin is crucial for energy production from carbohydrates, fats, and proteins. It also assists in the metabolism of other vitamins, including converting tryptophan to niacin (B3) and vitamin B6 to its coenzyme form. Because the body stores very little riboflavin and the excess is excreted in urine, a consistent daily intake from food or supplements is necessary to prevent deficiency.

Common Signs and Symptoms of Ariboflavinosis

Ariboflavinosis, the medical term for riboflavin deficiency, typically presents with a range of symptoms affecting the mouth, skin, and eyes. It's important to note that a deficiency in vitamin B2 often occurs alongside deficiencies in other B vitamins, so symptoms can sometimes overlap. The earlier signs are often reversible with treatment, but severe, prolonged deficiency can lead to irreversible changes.

Oral and Throat Manifestations

Cheilosis: The most characteristic sign, involving swollen, cracked lips, and painful, superficial fissures.
Angular Stomatitis: Painful cracks and sores that develop at the corners of the mouth.
Glossitis: The tongue may become sore and swollen, often appearing a distinctive magenta color.
Sore Throat: Inflammation and edema of the mouth and pharynx.

Skin and Hair Problems

Seborrheic Dermatitis: Greasy, scaly, and red patches can appear, particularly around the nose, mouth, ears, and eyelids, as well as on the genitals.
Hair Loss: A potential symptom associated with deficiency.

Ocular Symptoms

Photophobia: Increased sensitivity of the eyes to light.
Itchy, Red Eyes: Discomfort and redness of the eyes.
Blurred Vision: Vision problems can occur.
Cataracts: In severe and prolonged cases, cataracts can develop, which are anatomical changes that may not be fully reversed by supplementation.

Other Systemic Issues

Fatigue and Weakness: Due to its critical role in energy metabolism, low riboflavin can lead to a general lack of energy.
Anemia: A normochromic-normocytic anemia can develop.
Liver Degeneration: Severe deficiency can cause degeneration of the liver.
Neurological Degeneration: Degeneration of the nervous system is a possible effect of severe deficiency.

Causes and Risk Factors

Vitamin B2 deficiency can result from several factors, from simple dietary shortfalls to complex medical conditions.

Dietary Inadequacy

Poor Dietary Habits: Not eating enough riboflavin-rich foods, particularly dairy products, meat, and eggs, is a primary cause.
Vegan/Vegetarian Diets: Individuals who exclude dairy and meat may be at higher risk unless they consciously consume fortified cereals, nuts, and leafy greens.

Medical Conditions and Lifestyle Factors

Alcoholism: Chronic alcohol use impairs riboflavin absorption.
Malabsorption Syndromes: Conditions like celiac disease or chronic diarrhea prevent proper nutrient absorption.
Pregnancy and Lactation: Increased nutrient needs during these periods can put women at risk, especially if intake is low.
Genetic Disorders: Rare conditions like Riboflavin Transporter Deficiency (RTD) involve a genetic mutation that prevents the body from absorbing and transporting riboflavin effectively.

Diagnosis and Treatment

Diagnosis is typically based on clinical symptoms and a history of low intake. A healthcare provider can confirm riboflavin deficiency through urinary excretion tests or by monitoring symptom response to supplementation. Treatment is straightforward and involves increasing riboflavin intake, either through diet or supplements.

Foods Rich in Riboflavin

To correct and prevent deficiency, a diet rich in riboflavin is key. Some excellent sources include:

Beef liver and lean meats
Dairy products (milk, yogurt, cheese)
Eggs
Fortified cereals and breads
Mushrooms
Spinach and other green leafy vegetables
Almonds

Supplementation Guidelines

Oral Supplementation: Doses of 5 to 30 mg daily are often prescribed until symptoms resolve.
Severe Cases: In severe cases or malabsorption issues, intramuscular injections may be necessary.
Medical Supervision: It's crucial to consult a healthcare professional for proper diagnosis and dosing, as deficiency often coexists with other nutritional issues.

Dietary vs. Genetic Riboflavin Deficiency

While dietary deficiency is the most common cause of ariboflavinosis, a rare, inherited condition known as Riboflavin Transporter Deficiency (RTD) highlights the critical role of proper absorption and transport.


Feature	Dietary Riboflavin Deficiency	Riboflavin Transporter Deficiency (RTD)
Cause	Inadequate dietary intake or poor absorption.	Genetic mutation in riboflavin transporter genes (SLC52A2 or SLC52A3).
Severity	Symptoms are often reversible with dietary changes or supplements.	Can cause severe neurological symptoms, hearing loss, and respiratory difficulties.
Prevalence	Rare in developed countries due to fortified foods.	Very rare.
Onset	Gradual, due to chronically low intake.	Can begin in infancy or young adulthood.
Prognosis	Generally good, with symptoms resolving after treatment.	Can be fatal if untreated, though high-dose supplementation can be life-saving if started early.

Conclusion

When vitamin B2 is low, the body's energy production and cellular functions are compromised, leading to a range of recognizable symptoms affecting the mouth, skin, and eyes. While dietary causes are the most common and easily treatable, underlying conditions like malabsorption or rare genetic disorders can also lead to deficiency. Early diagnosis and intervention, typically through dietary adjustments and supplementation, can reverse many of the symptoms and prevent more severe, long-term complications like cataracts or neurological damage. For personalized advice, consult a healthcare provider. For more information on dietary sources, the NIH Office of Dietary Supplements offers a comprehensive fact sheet.

Frequently Asked Questions

The initial signs of vitamin B2 deficiency often appear around the mouth and eyes. These can include a sore throat, painful cracks at the corners of the mouth (angular stomatitis), swollen and red lips, and red, itchy eyes with sensitivity to light (photophobia).

The earlier symptoms of riboflavin deficiency are generally reversible with appropriate treatment. Recovery time varies based on the severity of the deficiency and the treatment method, but symptoms can begin to resolve within weeks or a few months of starting supplementation or dietary changes.

Excellent food sources of riboflavin include dairy products like milk, yogurt, and cheese, lean meats (especially organ meats like liver), eggs, almonds, and fortified grains and cereals. Some vegetables, such as mushrooms and spinach, also contain good amounts.

Yes, if left untreated for a long period, a severe riboflavin deficiency can lead to more serious health issues. These can include cataracts, anemia, and neurological degeneration. Some of these more severe anatomical changes may not be reversible with supplementation.

Riboflavin deficiency is considered extremely rare in countries like the United States due to the widespread fortification of grains and cereals. However, certain at-risk populations, such as individuals with malabsorption disorders, strict vegans, or pregnant women with low dairy intake, can still experience it.

Diagnosis of a riboflavin deficiency is primarily clinical, based on a patient's symptoms and dietary history. A doctor may also confirm the diagnosis with a therapeutic trial of riboflavin supplements or measure urinary riboflavin excretion.

A dietary deficiency is caused by insufficient intake from food and is usually resolved with dietary changes or supplementation. A genetic deficiency, or Riboflavin Transporter Deficiency (RTD), is a rare inherited disorder caused by a genetic mutation that prevents proper riboflavin absorption and transport.