Should I stop taking supplements before my blood test?

No, please keep taking your prescribed medications as usual – with a few exceptions on the morning of your blood draw. This allows us to assess your health in the context of your real-life routine.

Please include what you take and the dosage in your questionnaire so our medical team can interpret your results accurately.

On the morning of your test, please pause:

• Iron supplements: stop 24–48 hours before your draw – iron supplements temporarily raise circulating serum iron and can skew your results. Resume your usual dose right after the blood draw. (Fasting also matters for this – see our iron biomarker page for details.)
• Biotin (vitamin B7 – e.g. in hair, skin and nail supplements): at a standard dose (up to 5 mg/day), stop 48–72 hours before your test. It can interfere with several hormone measurements, including thyroid tests, causing falsely low TSH and falsely high free T4/T3. If you take high-dose biotin (over 5 mg/day – e.g. prescribed for hair/nail growth or another prescribed use), we generally recommend extending this to 3–7 days beforehand. Please don't do this without speaking to the doctor who prescribed it, and let us know in the medical questionnaire before your check-up. A standard multivitamin is fine to continue.
• Thyroid medication (e.g. levothyroxine): take it after your blood draw, not before – taking it beforehand causes a temporary spike in free T4 that affects your baseline result.

Also worth mentioning in your questionnaire:

• Creatine: may influence markers related to kidney function.
• Finasteride or dutasteride (e.g. for hair loss or an enlarged prostate): these lower PSA by about half, so if your check-up includes PSA (in the Pro package or as an add-on), flag this in your questionnaire so your result is interpreted correctly.