Low Vitamin B6: What Causes It and What Are the Symptoms?

Low vitamin B6 means your body may not have enough of a vitamin it needs for nerve function, making red blood cells and using energy from food. It is uncommon and usually linked to something else, such as heavy alcohol use, kidney disease, poor absorption or certain medicines. A low blood result is one piece of information that a clinician reads together with symptoms and history.

MedlinePlus explains that vitamin B6 helps the body make antibodies, supports normal nerve function, helps form haemoglobin in red blood cells, helps break down protein and helps keep blood glucose in a normal range. That wide role is why symptoms of deficiency can show up in the skin, mouth, nerves, mood and blood count.

This guide is for adults who have a low vitamin B6 result or are worried about deficiency. It cannot diagnose you or tell you whether you need treatment.

Healthdirect notes that severe vitamin B6 deficiency can cause nerve damage or, rarely, seizures, particularly in infants. A seizure from any cause can be serious.

The NHS advises calling emergency services for a seizure if:

• It is the first time someone has had a seizure.
• It lasts longer than is usual for them, or more than 5 minutes if you do not know how long their seizures usually last.
• The person does not regain full consciousness, or has several seizures without regaining consciousness.
• The person is seriously injured or has difficulty breathing after the seizure.

The NHS advises seeing a GP about early signs of nerve problems, such as pain, tingling or loss of feeling in the feet, loss of balance or weakness, or a cut or ulcer on the foot that is not healing.

Also arrange a prompt appointment if you have new confusion, low mood that is getting worse, or symptoms of anaemia such as unusual tiredness, especially if you drink heavily, have kidney disease or have recently started a new medicine.

Tingling, numbness and mood changes have many possible causes besides low B6, including diabetes, low B12 and some medicines. That is why a clinician's assessment matters more than one blood result.

MedlinePlus notes that vitamin B6 deficiency is uncommon in the United States. According to the MSD Manual, diet alone rarely causes it except in severe malnutrition. Healthdirect and the MSD Manual list the causes and risk groups shown in the list below.

On medicines, the MSD Manual lists several groups that can deplete vitamin B6: some anti-seizure medicines, an antibiotic used to treat tuberculosis, a blood pressure medicine that widens blood vessels, corticosteroids, and a medicine used for rheumatoid arthritis and Wilson disease. Healthdirect and an NHS laboratory guide also name tuberculosis treatment as an example.

Do not stop or change any prescribed medicine without talking to your prescriber. Some medicines can be dangerous to stop suddenly. If you take one of these medicines, ask whether B6 is something your care team monitors and whether any change is needed.

• Alcohol dependence or alcohol use disorder.
• Chronic kidney disease. The MSD Manual notes that a lot of vitamin B6 can be lost during haemodialysis.
• Conditions that reduce absorption of nutrients from food (malabsorption).
• Poor food intake or protein-energy undernutrition.
• Certain medicines that reduce the body's stores of B6.

Early or mild deficiency may cause few or no symptoms. When symptoms happen, sources describe:

• Sore, red or swollen tongue, mouth sores and cracks at the corners of the mouth.
• A red, greasy, scaly skin rash.
• Irritability, low mood, depression or confusion.
• Numbness, tingling or prickling in the hands and feet (peripheral neuropathy).
• Anaemia, because B6 is needed to make haemoglobin.
• Seizures, which are rare.

Blood tests usually measure pyridoxal 5-phosphate (PLP), the active form of the vitamin. One NHS laboratory gives an adult reference range of 40 to 100 nmol/L, but ranges and units differ between laboratories, so compare your result with the range printed on your own report. That laboratory does not require fasting; follow the instructions from the service doing your test.

The MSD Manual notes that no blood test can clearly confirm deficiency on its own. Diagnosis usually rests on symptoms, likely causes, examination and sometimes the response to treatment. Because symptoms overlap with low B12 and low folate, these are often considered too.

The NHS laboratory guide adds that B6 deficiency can raise homocysteine and affect iron absorption, so a clinician may look at other blood results alongside the B6 level.

MedlinePlus and the NHS list good sources including poultry, pork, beef, fish such as tuna and salmon, peanuts and other nuts, soya beans, chickpeas and other legumes, wheatgerm, oats and whole grains, bananas, milk and some fortified breakfast cereals.

The NHS says most people can get the vitamin B6 they need from a varied diet. If deficiency is confirmed, treatment usually means correcting the underlying cause; the MSD Manual notes that supplements usually correct it. Ask your clinician before taking supplements, because too much B6 can also harm nerves (see our high vitamin B6 guide).

Take your result, with its units and reference range, to the appointment.

• What could be causing my low B6: diet, alcohol, kidney disease, absorption or a medicine?
• Do my symptoms fit with low B6, or could something else explain them?
• Should my B12, folate or blood count be checked as well?
• Could low B6 be affecting my blood count or other results on this report?
• Does any of my medicines need monitoring or review? Please do not change it without telling me.
• Should I take a supplement, and how long before a repeat test?

On SameCase, patients and verified doctors share de-identified cases. Seeing how others with low vitamin B6 and similar circumstances, such as kidney disease or long-term medicines, discussed their situation can help you notice details worth raising and questions to ask.

Other cases cannot diagnose you or predict how your result will change. Use them to prepare, then decide next steps with your own clinician.