Signs of vitamin B deficiency

Anemia is a term that many people are familiar with. It can cause fatigue, weakness, and pale skin. But often people don’t realize that iron deficiency is not the only cause of anemia. A deficiency in certain B vitamins (especially folate and B12) can also lead to a type of anemia, called megaloblastic anemia.

Megaloblastic anemia is characterized by the production of abnormally large immature red blood cells in the bone marrow, which results in low numbers of healthy fully-matured red blood cells in circulation (1).

In this article, we will discuss the symptoms, including anemia, that are associated with vitamin B deficiency.

What are B vitamins?
B vitamins are a class of water-soluble compounds that play important roles in health and wellness, particularly cell metabolism and synthesis of red blood cells. There are eight different B vitamins: B1 (thiamin), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folate), and B12 (cobalamin) (2).

What are the best sources of B vitamins?
The best sources of B vitamins are meat, eggs, fish, and dairy products, as well as leafy green vegetables and legumes for many B vitamins (with the notable exception of vitamin B12, which is generally not present in plant foods).

What are the roles of B vitamins? And what happens during deficiency?
B vitamins are essential for the functions of numerous enzymes throughout the body (2). Here is a quick overview of what each of the B vitamins does, and the symptoms that can occur when people are deficient in these important vitamins:

  • B1 (thiamin) is important for the growth and function of various cells. Symptoms of deficiency can include weight loss, confusion, muscle weakness, reduced immune function, and peripheral neuropathy (reduced feeling in hands and feet) (3).
  • B2 (riboflavin) is essential for cell growth, energy production, and the breakdown of fats, steroids, and medications. Symptoms of deficiency can include swelling and pain in the tongue, mouth, and throat, hair loss, anemia, and eye problems (4).
  • B3 (niacin) helps for the generation of energy, cholesterol, and fats, and the creation and repair of DNA. Deficiency can cause depression, headache, fatigue, hallucinations, a scaly skin rash, and constipation or diarrhea (5).
  • B5 (pantothenic acid) helps break down fatty acids and build fats. Deficiency symptoms can include headaches, fatigue, sleep issues, muscle cramps, nausea, and numbness or burn in the hands or feet (6).
  • B6 (pyridoxine) is important for the proper breakdown of proteins, carbs, and fats, maintenance of homocysteine levels, immune function, and brain health. Deficiency is usually in conjunction with a deficiency in another B vitamin (e.g., B9 or B12) and can cause anemia, skin conditions, depression, reduced immunity, and confusion (7).
  • B7 (biotin) is another B vitamin important for breaking down fats, carbs, and proteins from food. Deficiency symptoms can include thin hair, skin rashes, and brittle nails (8).
  • B9 (folate) is the natural form of this vitamin, while folic acid is the synthetic form that is added to foods and available as a supplement. It is essential for the formation of nucleic acids, protein metabolism, and the generation of red blood cells. Deficiency can cause megaloblastic anemia, which is characterized by weakness, fatigue, irregular heartbeat, shortness of breath, hair loss, pale skin, and mouth sores (9).
  • B12 (cobalamin) is also essential for red blood cell production and the formation of DNA, as well as the function and development of brain and nerve cells. B12 deficiency is the most common B vitamin deficiency and can cause megaloblastic anemia (with the same symptoms as described for B9), as well as nerve damage leading to numbness in the hands and legs, depression, and seizures in extreme cases (10).

What factors can increase the risk of deficiency?
Each of the B vitamins deficiency can have different factors that contribute to an increased risk, but the primary reasons are a non-balanced diet, malnutrition, excess alcohol consumption, drug and medication use, and health complications that affect absorption (e.g., Celiac disease). Other factors that can also influence the risk include thyroid issues (for B2), carcinoid syndrome (for B3), genetic variants (e.g., MTHFR variants can affect folate levels), pregnancy (particularly for folate), vegan diets (particular for B12 as it is only naturally found in foods from animal sources).

How can I determine if I have a deficiency?
A simple blood test is all that is required to diagnose a deficiency. We offer lab tests for the most common B vitamin deficiencies–folate and B12. These tests just require a simple self-collected finger-prick blood sample and results are available online as soon as testing is complete. We recommend discussing any abnormal results with your healthcare provider to determine the next steps to improve your health.

1. Anemia, Megaloblastic. Rare Disease Database, National Organization of Rare Disorders.
2. B Vitamins. The Nutrition Source, Harvard School of Public Health.
3. Thiamin – Vitamin B1. The Nutrition Source, Harvard School of Public Health.
4. Riboflavin – Vitamin B2. The Nutrition Source, Harvard School of Public Health.
5. Niacin – Vitamin B3. The Nutrition Source, Harvard School of Public Health.
6. Pantothenic Acid – Vitamin B5. The Nutrition Source, Harvard School of Public Health.
7. Vitamin B6. The Nutrition Source, Harvard School of Public Health.
8. Biotin – Vitamin B7. The Nutrition Source, Harvard School of Public Health.
9. Folate (Folic Acid) ­– Vitamin B9. The Nutrition Source, Harvard School of Public Health.
10. Vitamin B12. The Nutrition Source, Harvard School of Public Health.