Blood draw
Vitamin B6
Vitamin B6; nervous system and metabolism.
€ 36,00
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Vitamins, minerals and amino acids · Blood
Vitamin B6
The amount of vitamin B6 in the blood; a deficiency is rare, and too much from supplements can cause nerve damage.
At a glance
- Measured in blood
- In 3 test panels
- No special preparation
Explanation
Vitamin B6: what is measured?
Vitamin B6 is needed for breaking down and building amino acids, for making blood and for the functioning of nerves and the immune system. It is found in meat, fish, eggs, bread and grain products, potatoes, legumes, vegetables and dairy products. The liver converts the different forms into the active form pyridoxal phosphate, which is what the test usually measures. Unlike many other water-soluble vitamins, too much vitamin B6 over a long period can be harmful.
What can it detect?
- Too much vitamin B6 from supplements or multivitamins, with a risk of nerve damage in the hands and feet (peripheral neuropathy)
- Vitamin B6 deficiency with malnutrition, excessive alcohol use, kidney failure or use of isoniazid (a medicine against tuberculosis)
Result
What does the result mean?
Vitamin B6 too high
A raised vitamin B6 is caused by supplements or multivitamins containing vitamin B6; you cannot get too much from a normal diet. Too much B6 over a long period can cause nerve damage in the hands and feet (peripheral neuropathy), with tingling, numbness or pain. The Netherlands Pharmacovigilance Centre Lareb received reports of nerve symptoms even at daily doses of 12 milligrams or less, while supplements in the Netherlands may contain up to 21 milligrams per day. About a third of the people with symptoms reported recovering after stopping.
Vitamin B6 too low
A low vitamin B6 may point to a deficiency. According to the Netherlands Nutrition Centre (Voedingscentrum), a deficiency hardly ever occurs in the Netherlands. A deficiency can develop with malnutrition, excessive alcohol use, kidney failure, during pregnancy and breastfeeding, and with use of isoniazid. A long-term severe deficiency can cause anemia, nerve symptoms, reduced resistance to infection and skin changes around the eyes, nose and mouth.
After an abnormal result
With a raised value and nerve symptoms, the GP asks about all supplements and products containing vitamin B6, usually advises stopping them and checks whether the symptoms decrease; with persistent or severe symptoms, referral to a neurologist follows. The side effect can be reported to the Netherlands Pharmacovigilance Centre Lareb. With a low value, the GP looks for the cause, such as alcohol use, diet, kidney function or medicines.
Reliability
How reliable is the test?
A strongly raised value in someone who takes supplements fits too high an intake and matters mainly when there are nerve symptoms. Because Lareb also received reports at low doses, the supplement use weighs just as heavily as the result itself. In people without symptoms a result says little: a deficiency hardly ever occurs, and a raised value mainly reflects recent supplement use.
What can affect the result?
- A supplement or multivitamin in the days before the blood draw raises the value; the result then mainly reflects recent intake.
- Vitamin B6 breaks down in sunlight; the sample must be protected from light until it is measured, otherwise the value may come out too low.
- After stopping supplements the value drops, while nerve symptoms may persist.
- Reference values differ per laboratory.
Who it is for
Who is the test useful for?
Useful for
Useful with tingling, numbness or pain in the hands or feet in someone who takes supplements, multivitamins or other products containing vitamin B6. Also useful when a deficiency is suspected in risk groups, such as with excessive alcohol use, malnutrition, kidney failure or use of isoniazid. In healthy people without symptoms the result adds little.
How common is it?
According to the Netherlands Nutrition Centre (Voedingscentrum), a vitamin B6 deficiency hardly ever occurs in the Netherlands. Symptoms from too much vitamin B6 do occur: the Netherlands Pharmacovigilance Centre Lareb received 238 reports of nerve symptoms in people using products containing vitamin B6, 79 of them at a daily dose of 12 milligrams or less. How often a too-high value occurs in people who take supplements is not known.
Netherlands Nutrition Centre (Voedingscentrum) and the Netherlands Pharmacovigilance Centre Lareb
Drawbacks and risks
- A normal value can give false reassurance with nerve symptoms if someone stopped taking B6 supplements shortly before.
- A slightly raised value due to a multivitamin in someone without symptoms can cause unnecessary worry.
Get tested
Vitamin B6: test panels
Vitamin B6 is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.
Evidence
Sources
This explanation is based on Dutch guidelines and independent information. It is general information, not a diagnosis. Discuss an abnormal result with your GP.
More about risks and resultsMore explanations
Other tests: Vitamins, minerals and amino acids
- AC/FC ratio
- Acylcarnitine
- Alanine
- Antibodies against intrinsic factor
- Arginine
- Calcium
- Calcium (albumin-corrected)
- Carnitine, free
- Carnitine, total
- Coenzyme Q10
- Copper
- Folic acid