Andarine (S4)
S4 · Andarine
SARM with notable vision-related side effects; short half-life requiring divided dosing.
Key takeaways
- Short ~4-hour half-life means reported protocols split dosing twice daily.
- Human PK data don't exist; the plotter curve is built from canine data.
- Signature side effect is visual: yellow tint and night-vision problems at higher doses, reported as reversible on stopping.
- Never advanced to meaningful human trials; unapproved and WADA-prohibited.
Overview
What it is
Andarine (S4) is one of the earliest non-steroidal selective androgen receptor modulators, developed for muscle wasting and osteoporosis. Like other SARMs it aims for anabolic activity in muscle and bone with less androgenic effect on the prostate, but it never advanced to meaningful human trials.
Pharmacokinetics
The half-life is short, roughly 4 hours, which is why reported protocols split dosing twice daily. The PK data behind the plotter come from canine studies, so the human curve is a rough approximation.
Harm reduction
Andarine's signature side effect is visual: a yellow tint and impaired night vision at higher doses, reported as reversible on discontinuation. Testosterone suppression and liver enzyme shifts track with other SARMs. It's unapproved, WADA-prohibited, and human safety data essentially don't exist, so reported protocols are anecdotal and third-party testing plus bloodwork (LH, FSH, total T, ALT/AST) are the minimum safeguards.
Reported dosing protocols
Protocols reported in research literature and clinic/community use — informational context, not a dosing recommendation.
| Use case | Dose | Route | Frequency | Duration |
|---|---|---|---|---|
| Physique (community) | 25–50 mg split into 2 doses | Oral | Twice daily | 6–8 weeks |
Pharmacokinetic summary
- Model tier
- Advanced (t½ + Cmax + Tmax + F)
- Half-life
- 3.9 hours
- Cmax
- 513.45 ng/mL
- Tmax
- 0.0 days
- Bioavailability
- 50%
- Typical dose
- 12.5–50 mg
Harm reduction
- Aromatizes
- No
- Hepatotoxicity
- mild
- Injection frequency
- Oral, 2×/day
⚠ Known vision side-effect (yellow tint, night blindness) at higher doses.
Frequently asked questions
Why does andarine affect vision?
The exact mechanism isn't established, but users report a yellow tint and difficulty with night vision and light adaptation at higher doses. Reports consistently describe it resolving after discontinuation. It's the distinguishing side effect of S4 versus other SARMs.
Does andarine have human trial data?
Essentially none. Development never reached meaningful human trials, and the PK profile in the plotter comes from canine data. Dosing numbers circulating online are community convention built on animal data and anecdote.
Why twice-daily dosing for andarine?
The roughly 4-hour half-life means a single daily dose produces a sharp peak and near-complete washout within a day. Reported protocols split the daily amount into two doses to keep levels steadier, which the plotter shows directly.
References
- Andarine PK (canine) — Canine data, likely inaccurate in humans.
- Andarine pharmacokinetics study (canine), Steroids 2019 — Animal PK data underlying the plotter estimate; no human PK studies published.
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