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Biotin and Blood Tests: What to Tell Your Lab

The Dose Analysis

Does biotin affect blood tests? It can. The NIH Office of Dietary Supplements (ODS) says supplementing with biotin beyond recommended intakes can cause clinically significant falsely high or falsely low lab results, depending on the test. Many lab tests use biotin as part of their chemistry, so extra biotin in your blood can throw them off. The practical step is simple: tell the clinician who orders your test, and the lab, about every product you take that contains biotin.

Key takeaways

  • The NIH ODS says biotin intakes above recommended amounts can cause falsely high or falsely low results on some lab tests, which may lead to a wrong diagnosis.
  • The ODS names thyroid hormone tests, 25-hydroxyvitamin D and, citing the FDA, a troponin test for heart attack among the tests affected.
  • Biotin can be found in hair, skin and nail formulas, B-complex products and some multivitamins. Tell your clinician and the lab about all of them before a blood test.

Why biotin can change a lab result

Many blood tests, called immunoassays, use a strong natural pairing between biotin and a protein called streptavidin to catch and measure a hormone or other marker. The NIH ODS explains that very high intakes of biotin may interfere with tests that use this biotin-streptavidin technology. These tests are commonly used for hormones such as thyroid hormone and for other markers such as 25-hydroxyvitamin D. The result can look falsely normal or falsely abnormal.

The direction of the error depends on how the test is built. In a small 2017 study in JAMA, six healthy adults took 10 mg (10,000 mcg) of biotin a day for 7 days. The authors found interference in 9 of 23 tests that used biotin and streptavidin, and in none of the 14 tests that did not. Some competitive tests read falsely high and some sandwich tests read falsely low. The authors called it a preliminary study and said the interference showed up in some but not all of the biotin-based tests.

Which tests the sources name

  • Thyroid tests: the ODS describes case reports in which people taking 10 to 300 mg of biotin a day had results that falsely suggested Graves' disease and severe hyperthyroidism. It adds that even a single 10 mg dose of biotin interfered with thyroid function tests done within 24 hours.
  • Thyroid stimulating hormone and NT-proBNP: the ODS reports that the 2017 study found falsely low levels of thyroid stimulating hormone and of N-terminal pro-brain natriuretic peptide, a heart-failure marker.
  • Vitamin D: the ODS lists 25-hydroxyvitamin D among the markers measured with biotin-based tests.
  • Troponin: according to the FDA, as reported by the ODS, a patient with a high intake of supplemental biotin died after a troponin test, used to help diagnose a heart attack, gave a falsely low result. The FDA's troponin page says some test makers have reduced biotin interference but others have not, and that it has continued to receive reports of falsely low troponin results caused by biotin.

Not every test is affected, and test makers keep changing their methods. That is why the lab, not a list online, is the best place to ask about a specific test.

How much biotin is in food and supplements

Adults need very little biotin. The Food and Nutrition Board set an Adequate Intake of 30 mcg a day for adults (35 mcg during lactation), and the ODS lists it. The ODS lists the Daily Value on U.S. labels as 30 mcg too. The ODS says biotin deficiency is rare and that average intakes from food in other western populations are about 35 to 70 mcg a day.

The ODS lists the biotin content of these selected foods:

Food Biotin per serving
Beef liver, cooked, 3 ounces 30.8 mcg
Egg, whole, cooked 10.0 mcg
Salmon, pink, canned in water, 3 ounces 5.0 mcg
Pork chop, cooked, 3 ounces 3.8 mcg
Hamburger patty, cooked, 3 ounces 3.8 mcg
Sunflower seeds, roasted, 1/4 cup 2.6 mcg
Sweet potato, cooked, 1/2 cup 2.4 mcg
Almonds, roasted, 1/4 cup 1.5 mcg
Tuna, canned in water, 3 ounces 0.6 mcg
Spinach, boiled, 1/2 cup 0.5 mcg
Broccoli, fresh, 1/2 cup 0.4 mcg
Cheddar cheese, mild, 1 ounce 0.4 mcg
Milk, 2%, 1 cup 0.3 mcg
Plain yogurt, 1 cup 0.2 mcg
Oatmeal, 1 cup 0.2 mcg
Banana, 1/2 cup 0.2 mcg
Whole wheat bread, 1 slice 0.0 mcg
Apple, 1/2 cup 0.0 mcg

Supplements are different. The ODS says biotin comes in biotin-only products, B-complex products and some multivitamins, and that free biotin taken by mouth is absorbed at a rate of 100%, even at doses up to 20 mg a day. The Food and Nutrition Board set no tolerable upper intake level (UL) for biotin, because there is no evidence in humans that it is toxic at high intakes. Lab test interference is the risk the ODS highlights instead, and it says intakes potentially even above the Adequate Intake may pose that risk.

What to tell your clinician and the lab

  • List every supplement before a blood test, including hair, skin and nail products, B-complex formulas and multivitamins. Read the Supplement Facts panel for a biotin line, because a product name may not mention it.
  • Give the amount per serving and how many servings you take a day.
  • Ask whether biotin could affect the tests ordered and whether you should change anything before the blood draw. Do not stop or change a prescribed medicine on your own.
  • If a result does not fit how you feel, mention biotin again. The ODS says the FDA advises health care providers to ask patients about supplements that contain biotin and to consider biotin interference when results do not match the clinical picture.
  • In an emergency, tell the care team about biotin as soon as you can.

Reading a high-biotin supplement label

Beauty Within+™ is an example of a hair, skin and nail formula with a large biotin amount. Its Supplement Facts list 5,000 mcg of biotin per 2-capsule serving, shown as 16,667% of the Daily Value. That is 5 mg, half of the 10 mg daily amount in the 2017 study, and no study cited here tested this product. The ODS says intakes above recommended amounts may cause lab interference, so a 5,000 mcg product is one to mention before any blood test.

The same serving lists vitamin A (as beta-carotene) 120 mcg RAE, vitamin C 120 mg, vitamin D (as cholecalciferol) 20 mcg, vitamin E (as DL-alpha tocopheryl acetate) 14 mg, thiamin 6 mg, vitamin B6 8 mg, folate 1,496 mcg DFE (880 mcg folic acid), vitamin B12 (as cyanocobalamin) 12 mcg, pantothenic acid 30 mg, calcium 80 mg, iron (as ferrous fumarate) 14.5 mg, magnesium (as magnesium oxide) 120 mg, zinc (as zinc oxide) 7 mg, manganese 4 mg and potassium 94 mg, plus a 359 mg proprietary blend. Blend totals are on the label; the amounts inside each blend are not. The label says "Contains: Soy," and the product page notes that the blend's barley grass contains gluten. There are 60 capsules, or 30 servings, per bottle.

Its suggested use reads: "For adults only. Take two (2) capsules daily. Do not exceed the recommended dose." The label caution reads: "Women who are pregnant or lactating and anyone taking medications should consult a health care professional before using any nutritional product. If any adverse reactions occur, discontinue use and consult a health care professional." The label also says: "Keep out of reach of children. Do not use if safety seal is damaged or missing. Store in a cool, dry place." Its iron warning says that accidental overdose of iron-containing products is a leading cause of fatal poisoning in children under six, and that in case of accidental overdose you should call a doctor or poison control center immediately.

Add it up before you combine products

Biotin has no UL, but other nutrients in a formula like this do. If you also take a multivitamin, a B-complex or fortified foods, add the totals. These are the adult upper limits listed by the NIH ODS, compared with one serving of Beauty Within+:

  • Folic acid: 880 mcg. Adult UL 1,000 mcg a day for folate from supplements or fortified foods. The ODS folate fact sheet also notes that large amounts of folate can correct the anemia, but not the nerve damage, of vitamin B12 deficiency.
  • Iron: 14.5 mg. Adult UL 45 mg a day.
  • Zinc: 7 mg. Adult UL 40 mg a day.
  • Vitamin D: 20 mcg. Adult UL 100 mcg (4,000 IU) a day.
  • Magnesium: 120 mg. Adult UL 350 mg a day, which counts magnesium from supplements and medicines only, not food.
  • Vitamin B6: 8 mg. Adult UL 100 mg a day. The ODS also notes that the European Food Safety Authority set a lower limit of 12 mg a day for all adults in 2023, based on peripheral neuropathy.
  • Vitamin C: 120 mg. Adult UL 2,000 mg a day from food and supplements.
  • Vitamin E: 14 mg. Adult UL 1,000 mg a day, which applies to all forms of supplemental alpha-tocopherol.
  • Calcium: 80 mg. Adult UL 2,500 mg a day for ages 19 to 50 and 2,000 mg a day for ages 51 and older, from food and supplements.
  • Manganese: 4 mg. Adult UL 11 mg a day.
  • Vitamin A: the ODS UL of 3,000 mcg a day applies to preformed vitamin A (retinol and its esters). The vitamin A on this label is listed as beta-carotene.

Medicines and other cautions

The NIH ODS fact sheets name medicines that interact with nutrients in a formula like this one:

  • Biotin: anticonvulsants such as carbamazepine, primidone, phenytoin and phenobarbital have been linked with lower biotin levels.
  • Iron: iron supplements may interact with levodopa and levothyroxine, and proton pump inhibitors can reduce iron absorption.
  • Hereditary hemochromatosis: the ODS iron fact sheet says the American Association for the Study of Liver Diseases recommends that treatment of hemochromatosis include avoiding iron and vitamin C supplements, and the ODS vitamin C fact sheet says high doses of vitamin C could worsen iron overload in this condition. This formula contains both iron and vitamin C.
  • Zinc: zinc may interact with quinolone and tetracycline antibiotics and penicillamine, and some diuretics can lower zinc levels.
  • Folate: folate supplements can interact with methotrexate, with antiepileptic drugs such as phenytoin, carbamazepine and valproate, and with sulfasalazine.
  • Vitamin D: the ODS names orlistat, statins, steroids and thiazide diuretics.
  • Magnesium: magnesium may interact with oral bisphosphonates, tetracyclines and quinolone antibiotics, and diuretics and proton pump inhibitors can affect magnesium status.
  • Vitamin B6: the ODS names the tuberculosis antibiotic cycloserine, antiepileptic drugs such as valproic acid, carbamazepine and phenytoin, and theophylline.
  • Vitamin C: vitamin C supplements may interact with radiation therapy, chemotherapy and statins.
  • Vitamin E: vitamin E supplements can interact with anticoagulants and antiplatelets, simvastatin and niacin, and possibly with chemotherapy and radiotherapy.
  • Vitamin A and beta-carotene: the ODS says the weight-loss medicine orlistat can decrease the absorption of vitamin A, other fat-soluble vitamins and beta-carotene.
  • Calcium: calcium supplements may interact with dolutegravir, levothyroxine, lithium and quinolone antibiotics.

If you take any of these, or any regular medicine, talk with your healthcare provider before use.

If you are pregnant, nursing or trying to conceive, ask your healthcare provider before use.

Frequently asked questions about biotin and blood tests

Can biotin cause a false thyroid test result?

Yes. The NIH Office of Dietary Supplements describes case reports in which high biotin intakes produced thyroid results that falsely suggested an overactive thyroid, and says a single 10 mg dose interfered with thyroid function tests done within 24 hours. Tell your clinician and the lab about any biotin you take.

Does the amount of biotin matter?

The studies and case reports the NIH ODS describes used 10 mg (10,000 mcg) a day or more, but the ODS says intakes above recommended amounts, and potentially even above the 30 mcg Adequate Intake, may cause lab interference. Mention any biotin-containing product, whatever the amount.

Which supplements contain biotin?

The NIH ODS says biotin is sold alone, in B-complex products and in some multivitamins. Hair, skin and nail formulas often list it too. Check the Supplement Facts panel of each product for a biotin line.

Should I stop biotin before a blood test?

Ask the clinician who ordered the test or the lab. They know which method the lab uses and can tell you whether any change is needed. Do not stop or change a prescribed medicine on your own.

Is a large amount of biotin toxic?

The Food and Nutrition Board set no upper limit for biotin because there is no evidence in humans that it is toxic at high intakes, according to the NIH ODS. The main risk the ODS describes is misleading lab results.

Related reading

Sources

The Dose Analysis and CuraMyHealth are both operated by Hofer LLC. Purchases linked from our reviews take place on CuraMyHealth.

This article is for education and is not personal medical advice. A qualified healthcare professional can help assess your needs and review the specific formula. Individual results vary.

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

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