Do you feel tired, irritable, find it harder to concentrate, or keep getting mouth ulcers and cracked mouth corners? One possible cause is an insufficient intake of one of the B vitamins. A mild deficiency can go unnoticed for a long time, but a significant or long-term lack of some B vitamins can lead to anaemia, neurological problems or developmental disorders. The risk also differs depending on age, diet, health status and the medications you take.
In this article, you will learn what the symptoms of B vitamin deficiency are, where to find B vitamins, who is most at risk and how to support an adequate intake.
What will you learn in this article?
- What are the symptoms of B vitamin deficiency
- Which B vitamins are most often linked to deficiency
- Where B vitamins are found
- How to recognise B vitamin deficiency and which tests are used
- Who is most at risk of B vitamin deficiency
- B vitamins in children
- How to ensure an adequate intake of B vitamins
- Key takeaways
What Are the Symptoms of B Vitamin Deficiency?
Each B vitamin has its own specific functions in the body, but a deficiency often leads to similar general symptoms. Read more about why B vitamins are the invisible engines of our cells.
The most common symptoms of B vitamin deficiency include:
- fatigue, weakness and a lack of energy,
- impaired concentration and memory,
- irritability or mood changes,
- pallor and anaemia,
- cracked mouth corners, inflammation of the tongue or mucous membranes,
- mouth ulcers and other changes in the mouth,
- skin changes,
- hair loss and brittle nails,
- tingling, numbness or burning in the limbs,
- sensory and coordination problems,
- digestive issues or reduced appetite.
The specific symptoms, however, depend on which vitamin is missing and how severe the deficiency is. For example, B12 deficiency can cause neurological problems and megaloblastic anaemia, while B6 deficiency may be associated with dermatitis, an inflamed tongue or cracked mouth corners.
If you experience long-term fatigue, neurological problems or recurring changes to your skin and mucous membranes, do not automatically assume a B vitamin deficiency. Similar symptoms can have many other causes.
Which B Vitamins Are Most Often Linked to Deficiency?
Not all B vitamins carry the same risk of deficiency. Vitamin B12, folate (B9) and vitamin B6 deserve particular attention, because a deficiency in these can have more significant health consequences.
Vitamin B12: why does a deficiency matter?
Vitamin B12, also known as cobalamin, contributes to normal red blood cell formation and to the normal functioning of the nervous system, and it has a role in the process of cell division.
A deficiency can develop not only from low intake but also from absorption problems. In natural foods, vitamin B12 is found mainly in animal products. However, B12 can also be obtained from foods fortified with this vitamin or from dietary supplements.
People at higher risk of deficiency include:
- vegans and some vegetarians,
- older adults,
- people with diseases of the stomach or small intestine,
- people who have had certain digestive tract surgeries,
- people with pernicious anaemia,
- people taking certain medications long term, such as metformin or proton pump inhibitors.
What are the signs of vitamin B12 deficiency?
B12 deficiency can cause:
- fatigue and weakness,
- megaloblastic anaemia,
- pallor,
- an inflamed tongue,
- tingling or numbness in the limbs,
- balance and coordination problems,
- changes in memory and cognitive function,
- mood changes.
Importantly, neurological symptoms can appear even without significant anaemia. If a deficiency goes untreated for a long time, some neurological consequences may be difficult to reverse.
Vitamin B9: folate and folic acid
Vitamin B9 refers to a group of substances that includes folate and folic acid. Folate has a role in the process of cell division and contributes to normal blood formation.
It is found naturally in, for example:
- dark green leafy vegetables,
- legumes,
- nuts,
- eggs,
- some fruits,
- seafood,
- liver and other foods.
The need for folate increases significantly during pregnancy, when folate contributes to maternal tissue growth and supports the rapid cell division involved in foetal development. Women who could become pregnant are advised to take 400 µg of folic acid daily from supplements and/or fortified foods, in addition to the folate in their usual diet. During pregnancy, the recommended folate intake is 600 µg DFE per day.
Folate deficiency can lead in particular to:
- megaloblastic anaemia,
- fatigue and weakness,
- shortness of breath,
- changes in the mucous membranes,
- impaired cell division.
During pregnancy, an adequate folate intake is also essential for reducing the risk of neural tube defects in the foetus. You can learn more in the article Folate – the health gem you might be missing.
Vitamin B6: how is it linked to the nervous system?
Vitamin B6 is involved in more than 100 enzymatic reactions in the body. It contributes to normal protein and glycogen metabolism, to the normal functioning of the nervous system and the immune system, and to normal red blood cell formation.
It is found, for example, in:
- fish,
- poultry,
- liver,
- potatoes,
- legumes,
- some fruits.
Vitamin B6 deficiency is relatively rare in the healthy population. The risk increases, for example, in people with absorption disorders, certain kidney diseases or alcohol dependence. Some medications can also contribute to a deficiency.
Signs of a more pronounced deficiency include:
- anaemia,
- skin changes,
- cracked mouth corners,
- an inflamed tongue,
- depression or confusion,
- weakened immune function.
It is also worth noting that with vitamin B6, more is not always better. Long-term high doses of vitamin B6 from supplements can actually damage the peripheral nerves.
Even a mild deficiency can disrupt mental balance!
Where Are B Vitamins Found?
B vitamins are naturally present in a wide range of foods. That is why a varied diet combining animal and plant sources is the best foundation.
Foods rich in B vitamins
- meat and organ meats,
- fish and seafood,
- eggs,
- dairy products,
- legumes,
- whole grains,
- nuts and seeds,
- leafy vegetables,
- potatoes,
- some fruits,
- nutritional yeast and other fortified foods.
However, individual foods contain different B vitamins. For example, vitamin B12 is found naturally mainly in foods of animal origin, while folate is abundant in leafy vegetables and legumes. Vitamin B6 is available in many foods, including fish, poultry, potatoes and some fruits.
That is why it makes little sense to talk about a single "B vitamin food". What matters much more is a varied diet.
How to Recognise B Vitamin Deficiency and Which Tests Are Used?
Properly diagnosing and evaluating a B vitamin deficiency can be more complex than it first appears. Blood tests are a common screening tool, but they often detect only one form of the vitamin, which may not reflect the actual status in the cells.
For example, a standard B12 blood test measures the total amount of this nutrient in the blood but does not show how much of it is actually active and usable by the body. This can lead to falsely "normal" results despite a real deficiency. A more accurate picture of B12 status can be provided by additional tests such as active B12 (holotranscobalamin), methylmalonic acid or homocysteine levels.
Homocysteine is one of the more sensitive markers of functional deficiency, particularly for vitamins B6, B9 (folate) and B12. Elevated homocysteine levels may indicate that one of these vitamins is missing or poorly absorbed, even if their individual blood levels appear normal.
To assess a B vitamin deficiency, we therefore recommend looking at the overall clinical symptoms together with medical history and a nutritional profile.
Who Is Most at Risk of B Vitamin Deficiency?
Vegans and vegetarians (on average, 80–90% of people following this diet have a vitamin B12 deficiency)
Older adults (due to impaired absorption)
People with digestive disorders
Pregnant and breastfeeding women (due to increased nutritional demands)
People experiencing chronic emotional stress or taking certain medications such as metformin, hormonal contraceptives, proton pump inhibitors, antibiotics or antidepressants
B Vitamins in Children
Children need B vitamins just like adults, but their needs are adapted to their age and stage of growth.
B vitamins are involved in:
- energy-yielding metabolism,
- nervous system development,
- red blood cell formation,
- normal immune function,
- the metabolism of proteins, carbohydrates and fats.
For example, vitamin B6 contributes to the normal functioning of the nervous system and the immune system.
For children, the most important thing is a varied diet appropriate for their age. If a child eats meat, eggs, dairy products, grains, legumes, vegetables and other varied foods, they get most of their B vitamins from these.
When should you pay attention to vitamin B12?
Particular attention should be paid to the diet of children who eat no or almost no animal foods.
Children on a vegan diet need a reliable source of vitamin B12 in the form of a suitable dietary supplement. In children, it is especially important to address a B12 deficiency early, because vitamin B12 is essential for the development of the nervous system.
It is not advisable to give children high doses of a B complex without a specific reason. The need for individual vitamins changes with age, and for some vitamins an excessive intake can also be undesirable.
How to Ensure an Adequate Intake of B Vitamins?
The foundation is a varied diet that regularly includes different sources of B vitamins.
It can help, for example, to:
- alternate different types of meat and fish,
- include eggs and dairy products,
- eat legumes regularly,
- choose whole grains,
- include nuts and seeds,
- eat plenty of vegetables, especially leafy greens,
- on a vegan diet, ensure a reliable source of vitamin B12.
When can taking supplements make sense?
Supplementation can be appropriate when your nutrient needs cannot be covered by your usual diet, or when there is an increased risk of deficiency in a specific vitamin.
A suitable supplement should contain reasonable amounts of the individual B vitamins and, ideally, forms that the body can use efficiently.
Key Takeaways
B vitamin deficiency can show up in many ways: from subtle but unpleasant symptoms to more serious health problems.
Common symptoms include fatigue and low mood: a deficiency can also show up as mouth inflammation, skin problems or neurological symptoms.
Blood tests can support the diagnosis: especially for vitamins B9 and B12, but results should always be interpreted in the context of other symptoms and markers.
Some groups have a higher risk of deficiency: these include pregnant and breastfeeding women, children, athletes, seniors, vegans and vegetarians, people under stress and people with digestive disorders.
A deficiency can be addressed through diet and suitable supplementation: a higher intake of foods rich in B vitamins and quality supplements with active forms of B vitamins can help, for example Daily F20 Complex.
Sources:
[1] Healthline. Symptoms of Vitamin B Deficiency. Updated August 27, 2024. https://www.healthline.com/health/symptoms-of-vitamin-b-deficiency
[2] NutraBio. B Vitamins: What They Mean for Athletes, How Much and Where to Find Them. https://nutrabio.com/blogs/endurelite/b-vitamins-what-they-mean-for-athletes-how-much-and-where-to-find-them
[3] Axe J. 10 Signs You Have a B Vitamin Deficiency (How to Boost B Vitamins Naturally). Updated February 28, 2025. Dr. Josh Axe – 10 Signs You Have a B Vitamins Deficiency (How to Boost B Vitamins Naturally)
[4] Noah L, Pickering G, Mazur A, et al. Effect of magnesium and vitamin B6 supplementation on mental health and quality of life in stressed healthy adults with low magnesemia: post-hoc analysis of a randomized controlled trial. Stress and Health. 2021;37(5):1000–1010. doi:10.1002/smi.3041. https://pmc.ncbi.nlm.nih.gov/articles/PMC9292249/
