The Claim
Oral melatonin has an absolute bioavailability of approximately 15% due to poor gastrointestinal absorption and significant first-pass hepatic metabolism, leading to systemic exposure levels that can be ten times higher than the body's natural nightly production when taken at standard supplement doses.
What the research says
Supports is higher
Support is ahead, but a single strong opposing study can change this.
These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.
When you take a melatonin pill, your body only absorbs about 15% of it because most of it gets broken down by your liver before it enters your bloodstream. Even so, the amount that does get absorbed can still be up to ten times more than what your body naturally makes at night.
See the scientific wording
Oral melatonin exhibits approximately 15% absolute bioavailability due to limited gastrointestinal absorption and extensive first-pass hepatic metabolism, resulting in systemic exposure that can exceed endogenous nightly production by tenfold at standard supplement doses.
What the research says
1 studyStudy: Pharmacokinetics of melatonin in man: first pass hepatic metabolism.
The study confirms that oral melatonin is heavily broken down by the liver before entering the bloodstream, which lowers its absorption but still allows supplement doses to create much higher blood levels than the body naturally produces overnight.
Related videos
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.