Hydroxylysine

Amino-acid

What is it

Hydroxylysine is a modified amino acid found primarily in collagen, where it stabilizes the triple-helix structure and provides attachment sites for cross-linking. It is produced in the body by post-translational hydroxylation of lysine.

Evidence for 1 use

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Collagen synthesis support

Limited Evidence

Hydroxylysine is required for collagen structure, but dietary intake rarely limits collagen synthesis. Adequate vitamin C and protein matter more.

How it works

Lysyl hydroxylase converts lysine residues to hydroxylysine in newly synthesized collagen, using vitamin C and iron as cofactors. Hydroxylysine residues are then glycosylated and serve as cross-linking sites that give mature collagen its tensile strength. Hydroxylysine is rarely supplemented as a free amino acid; instead, collagen peptide products deliver short peptides that include hydroxylysine residues. The body assembles its own collagen from individual amino acids, with hydroxylation occurring post-translationally.

Dosage

There is no RDA. As a component of collagen peptide supplements, hydroxylysine intake is small. Direct hydroxylysine supplementation does not have established therapeutic doses.

When and how to take it

If consuming collagen peptides, timing is flexible. Some protocols pair collagen with vitamin C for collagen synthesis support.

1 commercial form

Compare the main delivery options and what they’re best suited for.

Component of hydrolyzed collagen

Rarely sold as free amino acid; intake comes via collagen peptides.

Absorbed as small peptides.

Safety

Hydroxylysine in food and collagen supplements has a long safety record. Pure hydroxylysine supplementation has limited safety characterization.

Who should be cautious

No specific cautions beyond those that apply to collagen supplements broadly.

Interactions

No significant interactions reported.

Food sources

Bone broth and gelatin

Amount
200 mL
%DV
—

Frequently asked questions

Should I take hydroxylysine as a supplement?⌄

Not on its own. Collagen peptides plus vitamin C are the practical way to support collagen formation.

Why is hydroxylysine important?⌄

It stabilizes collagen and provides cross-linking sites that give tissues like skin and bone their strength.

References

Hydroxylysine on Wikidata — Wikidata link

Hydroxylysine on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on Hydroxylysine (PubMed search) — PubMed link

Track Hydroxylysine with Pilora

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.