Apparently healthy subjects, who take 10 mg/d of biotin at the same time each morning for 10 days. Blood draw for biobanking will be collected at baseline prior to starting biotin (day 1), after 10 days of biotin supplementation (day 10), and 10 days after participants stopped taking biotin (day 20).

Subjects under thyroid medication, who take 10 mg/d of biotin at the same time each morning for 10 days. Blood draw for biobanking will be collected at baseline prior to starting biotin (day 1), after 10 days of biotin supplementation (day 10), and 10 days after participants stopped taking biotin (day 20).

Apparently healthy subjects, who take 50 µg/d of biotin at the same time each morning for 20 days. Blood draw for biobanking will be collected at baseline prior to starting biotin (day 1), after 10 days of biotin supplementation (day 10), after 20 days of biotin supplementation (day 20), and 10 days after participants stopped taking biotin (day 30).

Daily intake of 10 mg or 50 µg per day

The study aims to assess the performance of specific biotinylated immunoassays after 10 days of ingesting 10 mg/d of biotin (high-dose), or 50 µg/d of biotin (low-dose). Control measurements will be performed at baseline (before biotin intake), and 10 days after last biotin intake.