ConditionHormones & metabolism
Vitamin B Deficiency: Signs, Causes and Treatment
Vitamin B deficiency means a shortage of one or more of the eight B vitamins, which the body needs to turn food into energy, make red blood cells and keep nerves healthy. The most common in practice are B12, folate (B9), thiamine (B1) and B6. Typical signs include fatigue, anemia, a sore red tongue, cracks at the mouth corners, numbness or tingling in the hands and feet, and memory problems. Most deficiencies are easily confirmed with blood tests and corrected with supplements.
Also called: B vitamin deficiency, B-complex deficiency, vitamin B complex deficiency
At a glance
- What it is
- Too little of one or more B vitamins: B1, B2, B3, B5, B6, B7, B9 (folate) or B12.
- Most common types
- B12 and folate (anemia, nerve damage), thiamine (heavy alcohol use), B6.
- Key symptoms
- Fatigue, anemia, sore tongue, mouth cracks, tingling or numbness, mood and memory changes.
- Main causes
- Poor diet, vegan diet (B12), alcohol, absorption problems, weight-loss surgery, some medicines.
- Treatment
- Supplements by mouth or injection; food sources; treating the cause.
When to get help
Call 911 or go to the ER
- Confusion, unsteady walking and abnormal eye movements, especially in someone who drinks heavily or has had prolonged vomiting (possible Wernicke encephalopathy, which needs IV thiamine immediately)
- Breathlessness at rest, chest pain or fainting with severe anemia
See a doctor within a day or two
- Numbness, tingling or weakness in the legs that is spreading, or new trouble walking or with balance
- Rapid memory loss or confusion in an older adult
- Severe fatigue with pale skin and a racing heart
Book a routine appointment
- Ongoing tiredness, a sore smooth red tongue or cracks at the corners of the mouth
- Pins and needles in the hands or feet
- Following a vegan diet without B12 supplements, or after weight-loss surgery
- Taking metformin or acid-reducing medicines long-term
Usually safe to manage at home
- Eating a varied diet with B-vitamin-rich foods, and taking a B12 supplement if you eat no animal products
What do B vitamins do?
The B vitamins are water-soluble, so the body stores little of most of them (B12 is the exception, with stores lasting years). They work together as helpers (coenzymes) in metabolism:
- Releasing energy from carbohydrates, fats and proteins
- Making DNA and new red blood cells
- Maintaining nerves and the brain
- Supporting healthy skin, mouth and eyes
Because many B vitamins come from the same foods, poor diet or alcohol misuse often causes several deficiencies at once.
Symptoms by B vitamin
| Vitamin | Main symptoms of deficiency | Common causes |
|---|---|---|
| B1 (thiamine) | Fatigue, irritability, nerve damage, heart failure (beriberi), confusion and unsteadiness (Wernicke encephalopathy) | Heavy alcohol use, severe vomiting, weight-loss surgery, malnutrition |
| B2 (riboflavin) | Cracks at mouth corners (angular cheilitis), sore magenta tongue, sore throat, scaly skin | Poor diet, alcohol, often with other B deficiencies |
| B3 (niacin) | Pellagra: the "3 Ds" of dermatitis in sun-exposed skin, diarrhea, dementia | Corn-based diets, alcohol, some medicines |
| B5 (pantothenic acid) | Burning feet, fatigue (very rare) | Severe malnutrition |
| B6 (pyridoxine) | Mouth sores, sore tongue, anemia, depression, confusion, neuropathy, seizures in infants | Alcohol, kidney failure, isoniazid and some other drugs |
| B7 (biotin) | Hair thinning, red scaly rash around eyes and mouth, brittle nails | Rare; eating many raw egg whites, genetic disorders |
| B9 (folate) | Megaloblastic anemia, fatigue, mouth ulcers, sore tongue; neural tube defects in pregnancy | Poor diet, alcohol, pregnancy, celiac disease, methotrexate |
| B12 (cobalamin) | Anemia, fatigue, numbness and tingling, balance problems, memory loss, depression, sore tongue | Pernicious anemia, vegan diet, older age, metformin, acid reducers, gut surgery |
For detailed guides, see vitamin B12 deficiency and folate deficiency.
Common signs of vitamin B deficiency
Mouth and tongue
A smooth, red, sore or swollen tongue (glossitis), mouth ulcers and cracks at the corners of the mouth are classic clues to deficiencies of B2, B3, B6, B9 or B12.
Blood
B12 and folate deficiencies cause megaloblastic anemia, with large, immature red blood cells. Symptoms include fatigue, pale skin, breathlessness and a fast heartbeat.
Nerves and brain
B12, B1 and B6 deficiencies damage nerves, causing peripheral neuropathy: tingling, burning or numbness starting in the feet. B12 deficiency can also damage the spinal cord, causing balance problems, and affect mood and memory. These nerve effects can become permanent if treatment is delayed.
Skin and hair
Rashes in sun-exposed skin (B3), scaly skin around the nose and mouth (B2, B6, biotin) and hair thinning (biotin) may occur.
Who is at risk?
- Older adults: reduced stomach acid lowers B12 absorption; about 1 in 20 people over 60 may be low in B12
- Vegans and some vegetarians: B12 is found almost only in animal foods
- People who drink heavily: alcohol impairs absorption and storage of thiamine, folate, B6 and others
- Pregnant and breastfeeding people: higher folate and B12 needs
- Digestive conditions: celiac disease, Crohn's disease, and after gastric bypass or stomach surgery
- Medicines: metformin and long-term proton pump inhibitors (B12), methotrexate and some antiseizure drugs (folate), isoniazid (B6)
- Pernicious anemia: an autoimmune condition that blocks B12 absorption
Diagnosis
- Complete blood count: looks for anemia and enlarged red cells
- Vitamin B12 and folate levels
- Methylmalonic acid and homocysteine: help confirm B12 deficiency when results are borderline
- Intrinsic factor antibodies: test for pernicious anemia
- Other B vitamin levels (B1, B6) in specific situations
- Nerve tests if neuropathy is present
Treatment
- B12: oral high-dose tablets work for most people, including many with absorption problems. Injections are used for pernicious anemia, severe deficiency or nerve symptoms.
- Folate: folic acid tablets, usually for about 4 months. B12 should be checked first, since folic acid alone can correct anemia while B12 nerve damage worsens.
- Thiamine: oral tablets for mild deficiency; urgent intravenous thiamine for suspected Wernicke encephalopathy, given before glucose.
- Other B vitamins: oral supplements as directed by your doctor.
- Treat the cause: dietary changes, alcohol treatment, managing gut conditions, reviewing medicines.
Energy usually improves within days to weeks. Anemia corrects over about 2 months. Nerve symptoms improve more slowly, over months, and may not fully recover.
A note on high doses
B vitamins are generally safe at normal doses, but long-term high-dose B6 (over about 100 mg a day) can itself cause nerve damage, and high-dose niacin can cause flushing and liver problems. Biotin supplements can interfere with many lab tests, including thyroid and heart tests, so tell your doctor before blood work.
Food sources of B vitamins
| Vitamin | Good sources |
|---|---|
| B1 | Whole grains, pork, legumes, fortified cereals |
| B2 | Milk, eggs, lean meat, mushrooms, fortified cereals |
| B3 | Poultry, fish, meat, peanuts, fortified grains |
| B6 | Poultry, fish, potatoes, chickpeas, bananas |
| Folate | Leafy greens, legumes, citrus, fortified bread and cereals |
| B12 | Meat, fish, eggs, dairy, fortified plant milks and nutritional yeast |
Frequently asked questions
What are the symptoms of vitamin B deficiency?
Common symptoms are tiredness, weakness, pale skin, a sore or smooth red tongue, mouth ulcers, cracks at the mouth corners, tingling or numbness in the hands and feet, low mood, irritability and memory problems. The exact pattern depends on which B vitamin is low.
Which vitamin B deficiency causes tingling in hands and feet?
Vitamin B12 deficiency is the most common cause of tingling and numbness from a vitamin shortage. Thiamine (B1) and B6 deficiency can also damage nerves. Paradoxically, taking very high doses of B6 for a long time can cause tingling too. A blood test can tell which is responsible.
What does vitamin B deficiency do to the tongue?
Several B deficiencies, especially B12, folate, B2, B3 and B6, can cause glossitis: a tongue that looks smooth, red or swollen and feels sore or burning. Cracks at the corners of the mouth and mouth ulcers often appear alongside. These signs improve after the deficiency is treated.
How long does it take to correct a vitamin B deficiency?
Energy and mood often improve within a few days to weeks of starting treatment. Anemia from B12 or folate deficiency usually corrects within about 2 months. Nerve symptoms take longest, improving over 6 to 12 months, and long-standing nerve damage may not fully recover.
Should I take a vitamin B complex supplement?
Most people who eat a varied diet do not need one. Supplements are useful for vegans (B12), people over 50 with low B12, pregnancy (folic acid), heavy drinkers, and people with absorption problems or on certain medicines. Ask your doctor to test levels first, because treatment depends on which vitamin is low.
Sources
This guide was written from current patient and clinical guidance, including:
- NIH Office of Dietary Supplements: Vitamin B12 Fact Sheet for Health Professionals
- NIH Office of Dietary Supplements: Thiamin; Riboflavin; Niacin; Vitamin B6; Folate Fact Sheets
- MedlinePlus: Vitamin B12 deficiency anemia
- NHS: Vitamin B12 or folate deficiency anaemia
- World Health Organization: Thiamine deficiency and its prevention and control in major emergencies