If you’re taking a supplement containing biotin (also called vitamin B7 or B8, vitamin H, or coenzyme R), commonly found in products promoting nail, skin and hair health, it is recommended that you wait at least 72 hours from your last dose before sample collection.
A ferritin test indicates if you your body is storing too much or too little iron. Your body needs iron to produce healthy red blood cells which carry oxygen from your lungs to the rest of your body.