Biotin supplements (Vitamin B7) are taken by many people to help with a range of problems. You'll find biotin in many multivitamins, particularly those aimed at improving hair and skin.
What many people don't know is that biotin can affect the results of blood tests. Modern tests often rely on antibodies binding to the biomarker that is being tested. Biotin is used in the test to help stick the antibody to the biomarker. So if you have higher than normal levels of biotin it will affect how the blood tests work.
Because the range of tests affected is so broad, and because the same test from different manufacturers can be affected in different ways it is safest just to assume that if you are taking biotin your results may be affected.
Generally, it is only people who are taking high dose supplements who are likely to be affected. Most of the research into biotin and its effect on blood tests is based on the blood levels of biotin rather than the dose. Different people will absorb and metabolise biotin at different speeds, so it is hard to say with confidence that a particular dose of biotin is safe to continue taking when having a blood test.
Having reviewed the available guidance, we advise customers to stop taking biotin supplements 48 hours prior to their blood test.
When someone stops taking biotin their levels will usually return to normal about 2 days after they stop taking it. This finding is based on research into relatively small numbers of people. It's not yet known whether this can be applied to the general population.
Biotin is starting to be used as a medicine, so if your doctor has advised you to take biotin then you should discuss whether it is safe to stop it prior to a blood test and how long they would recommend stopping it for.