Are there negative effects to taking biotin? The critical link to laboratory tests and other considerations

October 24, 2025 •

4 min read

While biotin is a water-soluble vitamin that is generally considered safe, a significant safety risk exists for those who take high-dose supplements. The primary negative effect is not toxicity, but the potential for biotin to cause misleading results in critical laboratory tests, which can lead to a misdiagnosis.

Quick Summary

Biotin is largely safe, but high-dose supplements can produce false results in lab tests for heart health, thyroid function, and more, which may lead to a misdiagnosis. Rare side effects like digestive upset may also occur, along with potential drug interactions.

Key Points

Lab Test Interference: High doses of biotin supplements can cause false results in many lab tests, including those for heart health and thyroid function.
FDA Safety Alert: The FDA has warned about biotin interference, and there have been reports of harm, including a death linked to false test results.
Rare Side Effects: While rare, high intake may cause mild side effects like digestive upset, skin rashes, excessive thirst, and insomnia.
Mitigation Strategy: Always inform your doctor and stop taking biotin for at least 72 hours before having blood work done to ensure accurate results.
Drug Interactions: Certain medications, such as some anticonvulsants, can lower biotin levels in the body.
Food vs. Supplements: Biotin from food is safe and sufficient for most people, whereas high-dose supplements carry specific risks not associated with dietary intake.

The Major Concern: Biotin Interference with Lab Tests

The most significant and well-documented negative effect of taking biotin supplements, particularly in high doses, is their interference with certain laboratory tests. The U.S. Food and Drug Administration (FDA) has issued a safety alert warning healthcare providers and patients about this risk, following reports of adverse events, including a death linked to a false negative troponin test result. This issue is especially relevant for people taking supplements marketed for hair, skin, and nail health, which often contain biotin amounts far exceeding the daily recommended intake.

How Biotin Causes Test Interference

Many common lab tests use biotin-streptavidin technology to detect various health markers. This is because biotin has a strong affinity for the protein streptavidin. When a test uses this technology, a lab marker (like a hormone) is tagged with biotin, and streptavidin is used to capture it for measurement. However, if a person has excessively high levels of biotin in their blood from supplementation, this extra biotin can compete for binding sites, leading to inaccurate test results. Depending on the specific test, this can cause a falsely high or falsely low reading.

Types of Laboratory Tests Affected

A wide range of tests can be compromised by high biotin levels, with potentially serious consequences for misdiagnosis and treatment. Affected tests include:

Thyroid Function Tests: Biotin can cause falsely low thyroid-stimulating hormone (TSH) and falsely high levels of T3 and T4. This can lead to a misdiagnosis of hyperthyroidism (overactive thyroid) or difficulty managing hypothyroidism.
Troponin Tests: These are crucial for diagnosing heart attacks. Biotin interference can cause a falsely low troponin level, which could lead to a missed or delayed diagnosis of a heart attack.
Reproductive Hormone Tests: Assays for hormones like follicle-stimulating hormone (FSH) and luteinizing hormone (LH) can also be affected.
Vitamin D Tests: Interference has been reported with some vitamin D level tests, potentially causing a falsely high result.

To mitigate this risk, healthcare providers generally recommend stopping biotin supplements for at least 72 hours before any lab work. It is crucial to inform all healthcare professionals about any supplements you are taking.

Potential Side Effects and Overdose

Unlike lab test interference, true toxicity from biotin is extremely rare. Since it is a water-soluble vitamin, excess amounts are typically excreted by the kidneys. However, some mild side effects have been reported, primarily associated with very high doses.

Less Common Side Effects

While not common, some individuals taking high doses of biotin may experience:

Digestive issues: Including nausea, stomach cramps, and abdominal pain.
Skin problems: Rashes have been reported, sometimes resembling psoriasis, particularly in allergic reactions.
Excessive urination and thirst: This is a known symptom of overdose, especially in diabetic patients, due to biotin's role in glucose control.
Insomnia: Trouble sleeping can be a symptom of an overdose.
Allergic reactions: While rare, allergic reactions can occur in hypersensitive individuals and may present as skin rashes, swelling, or breathing difficulties.

There have been very rare reports of more serious events, such as anaphylaxis, primarily with high intravenous (IV) doses.

Biotin Interactions with Medications and Lifestyle Factors

Biotin's effectiveness and levels can be influenced by other substances. Certain medications and lifestyle habits can affect how your body absorbs and utilizes this vitamin.

Anticonvulsant medications: Long-term use of certain anti-seizure drugs (e.g., carbamazepine, phenytoin, phenobarbital) can deplete biotin levels in the body.
Antibiotics: Extended use of antibiotics can potentially decrease biotin levels by affecting the gut bacteria that produce biotin.
Alcohol: Chronic alcohol use can interfere with biotin absorption and metabolism.
Smoking: Smoking has been shown to decrease biotin levels more quickly, which may require increased supplementation if necessary.

Who Should Exercise Caution?

While biotin deficiency is very rare, certain populations should be particularly mindful of their biotin intake and discuss supplementation with a healthcare provider. These groups include:

Individuals with a rare genetic disorder called biotinidase deficiency.
Pregnant and breastfeeding women, who have a higher biotin requirement.
Those with alcohol dependence or liver disease.
People with kidney disease or undergoing dialysis.
Patients with diabetes, as very high doses may affect blood sugar levels.

Comparison: Biotin from Food vs. Supplements


Feature	Biotin from Foods	Biotin from Supplements
Source	Naturally occurring in various foods like eggs, organ meats, nuts, seeds, and some vegetables.	Synthetic, sold as single vitamins, B-complex, or in high-dose beauty supplements.
Dosage	The amount is generally moderate and sufficient for daily needs in most people.	Can be extremely high (e.g., 5,000 to 10,000 mcg), thousands of times the recommended daily intake.
Safety	Consumed at natural levels, it is highly unlikely to cause any negative effects.	High doses can cause mild side effects and, more importantly, interfere with lab tests.
Health Impact	Contributes to overall nutrient intake and metabolism without carrying the risks associated with high supplementation.	High doses are often unnecessary for healthy individuals and carry the risk of misleading diagnoses.

Conclusion

When considering biotin, the primary distinction lies between the low, safe levels found in food and the extremely high doses common in supplements. For most people, a balanced diet provides all the biotin they need, with no associated risks. The most significant negative effect of biotin supplementation is its proven ability to interfere with a range of lab tests, potentially leading to misdiagnosis of serious medical conditions. While other side effects are rare, they can occur with excessive intake. It is essential to communicate with your doctor about all supplements you take, especially before any scheduled blood work, to ensure accurate test results and appropriate care. As with any dietary supplement, moderation and medical guidance are key.

For further reading, consult authoritative sources such as the NIH Office of Dietary Supplements fact sheet on biotin, which provides comprehensive information on dosage, food sources, and potential risks.

Frequently Asked Questions

The most serious negative effect is not toxicity, but the interference of high-dose biotin with critical laboratory tests. It can cause falsely low or high results for conditions like heart disease and thyroid issues, potentially leading to a misdiagnosis.

Yes, biotin interference can cause a falsely low reading on a troponin test, which is used to help diagnose heart attacks. This could lead to a missed or delayed diagnosis with potentially life-threatening consequences.

The standard recommendation is to stop taking biotin supplements for at least 72 hours (three days) before having blood work. However, the exact timing can depend on the specific test and dosage, so always consult your doctor.

While toxicity is very rare, excessive intake may cause mild side effects such as nausea, digestive cramping, skin rashes, excessive thirst, and insomnia.

Yes, some medications can affect your biotin levels. Anticonvulsants, in particular, can lower biotin levels in the body. It is always important to discuss all supplements with your doctor.

For most healthy individuals, getting biotin from a balanced diet is safer and sufficient. The high doses in many supplements are unnecessary and carry the risk of interfering with lab tests, a risk not present with food-based biotin.

Scientific evidence supporting the use of biotin for hair and nail growth in healthy people is limited. Benefits are typically only observed in cases of a true biotin deficiency, which is rare.