Ask the doctors: Excess biotin can skew lab tests

Dear Doctor: I’ve been taking biotin for my nails, but I’ve read that it can mess up the results of important lab tests. Should I stop taking it?

Dear Reader: Biotin is one of the eight B vitamins, each of which plays an essential role in cell function. Also known as vitamin B7, biotin helps the body break down and absorb fatty acids, glucose and amino acids. (Basically, energy production.) It’s also important in DNA repair, gene regulation and cell signaling.

Biotin is a water-soluble vitamin, which means it’s not stored in the body. However, it’s naturally available in a wide range of foods, including eggs, beef, dairy products, sunflower seeds, pork, salmon, brewer’s and nutritional yeast and organ meats. It’s also found in certain vegetables, including spinach, broccoli, cauliflower and sweet potatoes.

Although a minimum recommended daily requirement (RDA) for biotin has not been established, the National Academy of Sciences’ Food and Nutrition Board suggests adults get at least 30 micrograms of biotin per day, and that women who are breastfeeding aim for a minimum of 35 micrograms per day. A balanced and varied diet will naturally provide enough biotin.

Symptoms of a biotin deficiency include hair loss, brittle nails and skin rashes, which has led biotin supplements to be promoted for improved hair growth, stronger nails and better skin. The vitamin is used in veterinary medicine, where it has been shown to help heal the cracked hoofs of pigs and horses.

When it comes to human applications, only a few small studies have been done. In 1989, researchers found that 41 of the 45 women who completed a biotin study showed measurable improvement to the strength and firmness of their fingernails after taking 2.5 milligrams of the vitamin for about six months. Most of the positive reports about the effects of biotin are anecdotal.

Unfortunately, as you point out, biotin supplements can have grave and unintended consequences in lab tests. The biotin our bodies need is measured in micrograms. But the amount of biotin in many supplements comes in milligrams, in quantities that can be up to 650 times the RDA. High doses of the supplement can cause a range of lab tests, including one used to diagnose heart attack, to yield skewed results. This happens because certain lab tests use biotin as part of the testing method. Patients taking biotin supplements can get lab results that are too high or too low, which puts them at risk of being misdiagnosed or not receiving the proper treatment. In one case, a patient died because his biotin intake obscured the test results that would have shown he was having a heart attack.

Biotin is now added to so many multivitamins and supplements that you may be ingesting large amounts without even realizing it. People who take a biotin supplement should disclose this fact to their health care provider before undergoing tests. If you’re not sure, carefully read the labels of any supplements, particularly those marketed to help with nails, hair or skin. Because biotin is water-soluble, it takes just a few days to clear it from the body and thus be ready for accurate lab results.