Biotin (vitamin B7) test: what the result means

Biotin is a water-soluble B group vitamin (B7), also called vitamin H. It helps the body break down and use food for energy, it is essential for the production of fatty acids, and it takes part in carbohydrate and protein metabolism. The body gets part of its biotin from food — egg yolk, organ meats, nuts, legumes, milk, yeast — and part is produced by gut bacteria, so an additional source is usually not needed. A blood biotin test is done less often than tests for other vitamins, because widely recognised standardised reference ranges have not been established: different methods give different results, so the answer is most often assessed together with clinical signs rather than as an isolated number. Biotin deficiency is rare, because the vitamin is widespread in food and is additionally produced by the gut microflora, but it can occur under certain conditions and cause changes to the skin, hair and mucous membranes.

• When there is unexplained hair thinning or hair loss
• When a skin rash or dermatitis appears without a clear cause
• When there is muscle pain or swelling of the tongue (glossitis)
• When nails become brittle
• When assessing nutritional status after eating a restricted or unbalanced diet for a long time
• When assessing rare inherited metabolic conditions related to how the body uses biotin

There is no widely recognised standardised reference range for biotin in blood — different laboratory methods give different results, so the answer has to be assessed against the interval given by the particular laboratory and together with clinical signs. Your own result sheet is where the range that applies to you is printed, and what it means is for your doctor to weigh.

How much biotin is needed and where it comes from

Per the MedlinePlus encyclopedia, adults (19 years and older, including pregnant women) are advised to get about 30 micrograms a day, and breastfeeding women about 35 micrograms a day. Per the same encyclopedia, biotin is plentiful in egg yolk, organ meats (liver, kidneys), nuts, legumes, milk, pork, yeast and chocolate.

Per the MedlinePlus encyclopedia, no toxic effect on the body from an excess of biotin has been established. Per the United Kingdom health authority (NHS), taking up to 0.9 mg of biotin a day is considered unlikely to cause harm, but data on the effect of large doses is lacking.

Causes listed for a raised result:

• Large doses of biotin supplements (often taken for the condition of hair, skin or nails)
• Taking several multivitamin complexes, so that the total biotin dose adds up

What to discuss with a doctor:

• Discuss every food supplement you take with your doctor before any blood test
• If a thyroid or another hormone test is planned, tell your doctor about biotin supplements in advance
• The long-term effect of large doses has not been established — that is worth asking your doctor about

A low biotin result

Per the MedlinePlus encyclopedia, an insufficient amount of biotin can cause muscle pain, dermatitis or swelling of the tongue (glossitis), and also skin rashes, hair loss and brittle nails. A shortage occurs rarely, because biotin is plentiful in food and is produced by gut bacteria.

Causes listed for a low result:

• An inadequate and unbalanced diet
• Long-term consumption of raw egg white (the protein avidin it contains binds biotin and interferes with its absorption)
• Conditions that interfere with the absorption of nutrients in the gut
• Rare inherited metabolic diseases related to how biotin is used

Symptoms listed for a shortage:

• Muscle pain
• Dermatitis (inflammation of the skin)
• Glossitis — swelling of the tongue
• Skin rashes
• Hair loss
• Brittle nails

What to discuss with a doctor:

• An assessment of eating habits with your doctor or a dietitian
• Checking the status of other vitamins (B12, folic acid, B6), if a broader nutritional shortage is suspected
• An assessment of possible conditions of the digestive tract that interfere with absorption

See also

Related pages: vitamin B12 test, vitamin B1 test, vitamin B2 (riboflavin) test and active B12 test.