S-4

weak data

Also seen as: Andarine

The Dose Guy’s verdict

Sep 1, 2026
2 sources

S-4 is the old cutter. It hardens, it dries, and it gives some people a yellow tint in their vision that makes night driving an adventure. The problem is not that it fails to work. The problem is that the evidence is entirely animal studies, the vision side is real and dose-limiting, and ostarine does the cutting job with human data behind it and no eye effects. It is dated, and there is not a strong reason to reach for it over its better-studied siblings.

Would I take it?Caution, dated and outclassed.

What it is

S-4 is a first-generation nonsteroidal selective androgen receptor modulator, one of the earliest to come out of preclinical development. It was designed for osteoporosis and muscle wasting, and it never made it to a human trial. In rats it showed the SARM promise: anabolic in muscle and bone, lighter on the prostate than testosterone.

The community picked it up for cutting cycles because it dries and hardens without the water retention that comes with LGD-4033, and it is milder than RAD-140. But the shelf has moved past it. Ostarine covers the same territory with real human trial data, milder suppression, and no vision side effects. S-4 still has a following among people who like the look it gives, but the case for choosing it over the newer options has gotten thin.

What the research shows

No human trials. Zero. Everything below is animal or in-vitro work. Read it as “interesting,” not “evidence it works in you.”

There is no human data on S-4. The findings are from animal models and product analysis:

In castrated male rats treated for 8 weeks, S-4 at 3 and 10 mg/kg restored soleus muscle mass and strength and levator ani muscle mass to intact-animal levels.Endocrinology 2005 · rat study

In 120 ovariectomized female rats treated for 120 days, S-4 maintained whole-body and trabecular bone mineral density and cortical content while reducing body fat.J Bone Miner Res 2007 · rat study · n=120

No interventional human trial reporting S-4 efficacy, safety, or pharmacokinetics exists in the published literature.as of Aug 2026

Realistic protocols

People run S-4 at 25 to 50 mg a day, split into two or three doses because it clears fast. Eight weeks is a standard cycle. Start at 25 mg and hold for a week or two. The vision side is dose-dependent, and you will know quickly if you are one of the people it hits.

If you see a yellow tint or your night vision degrades, cut the dose. Some people drop to 25 mg on a five-days-on, two-days-off schedule, which the community reports reduces the vision issue without killing the effect entirely. If the vision changes do not clear within a few days of lowering the dose, stop.

Suppression is moderate, somewhere between ostarine and LGD-4033. A short PCT with a SERM for three to four weeks is standard, though some people at the lower dose range recover without one.

S-4 is WADA-banned. If you compete in a tested sport, this is a positive test.

A third-party COA is non-negotiable. One black-market liquid sold online as green tea extract and face moisturizer turned out to be roughly 150 mg/mL of S-4 with about 10% impurity from poor purification. That is the market you are buying from.

Weeks 1–825 mg/day splitTwo or three doses. Start here to test for the vision side.

If tolerated50 mg/day splitOnly if no vision changes at 25 mg. Most of the effect is at the lower end.

Vision protocol5 on / 2 offCommunity-reported schedule. If yellow tint appears, drop dose and cycle days. If it persists, stop.

PCTNolvadex 10–20 mgThree to four weeks. Lighter than RAD-140 or LGD-4033 recovery.

Side effects

One side effect defines this compound:

anecdotalYellow-tinted vision and degraded night vision, widely reported, dose-dependent, and reversible on cessation. The signature S-4 side that sends people elsewhere.

monitorTestosterone suppression. Expected from the mechanism and universally reported. Get bloodwork after the cycle.

monitorLipid changes are likely given the androgen-receptor activity. Run a panel after the cycle.

unknownNo human safety data exists. Every side-effect report is community-sourced, and the vision mechanism has never been studied in a person.

Where to buy

No live listings from tracked vendors right now.