High-Dose Biotin Distorts PSA, TSH and Troponin Tests — JCO 2026 Warning
A new clinical warning from the oncodermatology team at the Ohio State University Wexner Medical Center, published in JCO Oncology Practice and reported by ScienceDaily on May 7, 2026, says high-dose biotin (vitamin B7) commonly found in hair, skin and nail supplements can distort a wide range of immunoassay blood tests including PSA, TSH, estrogen, testosterone and cardiac troponin. The result is false negatives that delay detection of cancer recurrence and false positives that drive unnecessary procedures.
Researchers explain that biotin does not change actual hormone or marker levels. Instead, it hijacks the streptavidin-biotin binding step that many lab assays rely on. Clinicians and patients both struggle to spot it.
Biotin Is in More Supplements Than You Think
Where it shows up:
- Hair-loss supplements (5,000–10,000 μg per serving in most products)
- Nail strengtheners
- Multivitamins (200–300 μg)
- Anti-aging skin–hair–nail combination products
- An estimated 20% of US adults take some biotin-containing supplement
The dose problem:
- Recommended daily intake: 30 μg
- Typical hair supplement: 5,000–10,000 μg (166–333× RDI)
- True deficiency is extremely rare because gut microbes synthesize biotin
Tests Most Affected
1. PSA (prostate-specific antigen):
- Key marker for prostate cancer diagnosis and recurrence tracking
- Biotin can falsely lower PSA, masking recurrence
- Or falsely raise it, triggering unnecessary biopsy
2. TSH (thyroid-stimulating hormone):
- Used for hypothyroid and hyperthyroid diagnosis
- Falsely low TSH may mimic hyperthyroidism
- Risk of missing thyroid cancer recurrence
3. Estrogen, testosterone, SHBG:
- Menopause, PCOS and male hypogonadism assessment
- Hormone replacement therapy (HRT) dosing decisions
- Biotin can shift readings up or down unpredictably
4. Cardiac Troponin:
- Frontline ER marker for myocardial infarction
- Falsely low troponin can miss a heart attack
- Falsely high troponin can lead to invasive workups
5. Tumor markers:
- CA-125 (ovarian cancer), CA 15-3 (breast cancer)
- HCG (pregnancy and germ-cell tumors)
Anna Malagoli — “The numbers didn’t match how I felt”
The JCO Oncology Practice case series features a patient, Anna Malagoli, who took hair supplements long-term while undergoing hormone monitoring. Her labs were inconsistent and clinically incongruent. An oncodermatologist suspected biotin interference, ordered her to stop for 72 hours, and the repeat results normalized. “The results didn’t balance out,” Malagoli said in the report.
These cases happen but rarely get diagnosed. If clinicians do not ask about supplements, the distorted readings flow straight into treatment decisions.
Clinical Recommendations from Dr. Brittany Dulmage
Dr. Brittany Dulmage, lead author and oncodermatologist:
1. Stop biotin at least 72 hours before any blood test:
- Half-life is 1–2 hours, renally cleared
- 5,000–10,000 μg products need at least 72 hours
- Very high doses (20,000 μg+) may need a full week
2. Consider avoiding biotin altogether:
- Deficiency in well-fed populations is exceedingly rare
- Hair benefit data outside of true deficiency is weak
3. Hair-loss alternative — FDA-approved minoxidil:
- Topical minoxidil 2–5%: first-line for female pattern hair loss
- Low-dose oral minoxidil (1.25–2.5 mg/day): emerging option
- Evidence base far stronger than biotin
4. Disclose all supplements before labs:
- Multivitamins, hair-skin-nail combos and standalone biotin
- Coordinate the test order with the patient’s intake schedule
”Hair Vitamins Are Harmless” Is Half True
Biotin is water-soluble and not directly toxic — the “harmless” intuition isn’t wrong about toxicity. But the warning here is about diagnostic accuracy. Safe to swallow is not the same as safe during a workup. The clinical cost shows up as missed cancer recurrence and missed heart attacks.
What to Do Right Now
If a hormone, cancer marker or cardiac test is on your calendar, stop the hair supplement 72 hours before. Patients on HRT, in cancer surveillance or with thyroid disease should be even stricter. And given that a far better-evidenced hair-loss treatment (minoxidil) exists, relying on megadose biotin starts looking like the less rational choice.