Research
Hormonal
Oral melatonin supplements have poor absolute bioavailability (approximately 15%) due to poor absorption and first-pass metabolism, whereas intravenous administration shows similar half-life but higher immediate serum peaks.
If using melatonin supplements, be aware that oral bioavailability is low (~15%). This means a significant portion is lost to metabolism. Sublingual or liquid forms may have different profiles, but standard tablets require careful dosing. Food sources provide a slower, sustained release with antioxidant benefits.
GoodQualifiesHIGH confidence
This study revealed the poor absolute bioavailability of oral melatonin tablets in both dosages, which was approximately 15%, possibly because of the poor oral absorption, large first-pass metabolism, or combined.
Why this rating
Cites specific human studies with quantitative bioavailability data.
Source
Dietary Sources and Bioactivities of Melatonin
Xiao Meng et al. · Nutrients · 2017
DOI 10.3390/nu9040367
narrative_reviewCited 350×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
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