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Andarine, also called S4 or S-4, is an experimental selective androgen receptor modulator (SARM) that lifters mostly use on a cut. It has a reputation as a mild, “dry” SARM that holds on to muscle while fat comes off, and a side effect no other popular SARM is known for: a yellow tint to vision and trouble seeing in the dark.
Two claims about andarine still circulate, and neither holds up: that it does not suppress natural testosterone, and that it is safe under 50mg a day. No human trial of andarine has been published. Its effects on muscle, fat and bone come from rat studies; its effects on vision, from user reports.
This guide covers the research, vision side effects, suppression, reported doses, realistic results, women, and how S4 compares with other SARMs. Nothing here is a recommendation to use it.
Key Takeaways
- Andarine (S4) is an experimental SARM developed for muscle wasting, bone loss and prostate enlargement. It was never approved, and no human trial results have been published.
- In rats it restored muscle mass and strength, reduced body fat and protected bone, with a much weaker effect on the prostate.
- Users commonly report a yellow tint and poor night vision, more often at higher doses. The cause is unknown and long-term effects have never been studied.
- The claim that S4 does not suppress LH, FSH or testosterone is not supported. Like other SARMs studied in people, it should be expected to lower natural testosterone.
- Commonly reported cycles run 6 to 8 weeks at 25-50mg a day. These figures come from users, not clinical research, and product quality is unreliable.
What Is Andarine (S4)?
Andarine (development codes S-4 and GTx-007) is a non-steroidal SARM developed by GTx, Inc. with researchers at the University of Tennessee. It was built on the structure of bicalutamide, a drug that blocks the androgen receptor, and modified to activate the receptor instead. The goal was testosterone-like effects on muscle and bone with much less effect on the prostate, for conditions such as muscle wasting, osteoporosis and benign prostatic hyperplasia (an enlarged prostate).
GTx later moved its clinical work to a closely related compound, ostarine (enobosarm). Andarine was never approved, and what is sold online as S4 is labeled as a research chemical, “not for human consumption”.
How Andarine Works
Andarine binds to the androgen receptor, the same receptor testosterone acts on. In rats, it acted as a strong activator in muscle but only a partial one in the prostate. That is what “selective” means: a different balance of effects between tissues, not an effect on muscle alone. It still acts in the brain, skin and reproductive system, which is where suppression and androgenic side effects come from.
As a non-steroid, andarine is not converted to estrogen or DHT. Claims that it burns fat by lowering lipoprotein lipase (LPL) or “shedding water under the skin” have not been shown in people; the drier look users describe also matches dieting, which is how S4 is mostly used.
What the Research Actually Shows
The published evidence comes almost entirely from rats, mostly from the group that developed andarine:
| Research | Subjects | What It Found |
|---|---|---|
| Early pharmacology studies | Castrated male rats (animal data) | Restored an androgen-sensitive muscle close to normal weight, with a much smaller effect on the prostate |
| Prostate enlargement study | Intact male rats (animal data) | Lowered prostate weight, similar to finasteride, without shrinking muscle |
| Muscle and bone study | Castrated male rats (animal data) | Restored muscle mass and strength, reduced fat mass and prevented bone loss |
| Bone and fat study | Female rats with ovaries removed (animal data) | Prevented bone loss and reduced body fat |
| Trials in people | None published | No human data on muscle, fat, hormones, dosing, vision or safety |
Rats handle drugs differently from people, so these studies do not give a human dose or show how human hormones or vision respond. They also used pure compound, which an underground product does not guarantee.
Andarine Vision Side Effects
Vision changes set andarine apart from other SARMs. Everything below comes from user reports; no published study has examined its effect on the human eye.
What Users Report
- A yellow tint: white and light surfaces look yellowish, often most noticeable indoors or on screens.
- Poor night vision: slower adjustment from bright light to darkness and difficulty seeing in dim light, which makes night driving harder.
- Glare: some users describe bright light as harsher than usual.
The cause has not been established. A common explanation is that andarine or a breakdown product acts on the retina, but that is a hypothesis, not a finding. The reports are consistent enough that the effect is generally attributed to andarine itself.
Dose and Recovery
In user reports, vision changes are far more common at 50mg a day and above, which is where the “stay under 50mg” advice comes from. They are also reported at lower doses, so no dose is known to be free of them. Splitting the daily amount is often said to help; there is no data either way.
Users commonly report that vision returns to normal within days to a few weeks of stopping. But no one has followed users’ eyesight long term, and vision that seems normal is not an eye exam showing no change.
When to Stop and See a Doctor
Any change in vision while taking a research compound is a reason to stop and get it checked. Sudden vision loss, a shadow over part of your sight, new flashes or floaters, or eye pain need urgent care. Avoid night driving while your night vision is affected, and tell the doctor what you took.
Does Andarine Suppress Testosterone?
Older guides often say andarine does not suppress LH or FSH and needs no post-cycle therapy. There is no human evidence for that. The brain senses androgen activity and adjusts its output of LH and FSH, the hormones that tell the testes to make testosterone and sperm. Andarine activates the androgen receptor, so the brain should be expected to turn that output down.
No study has measured this with andarine, but other SARMs tested in humans show what to expect. In a 21-day trial of LGD-4033 in healthy young men, total testosterone, SHBG and HDL cholesterol fell in a dose-dependent way, with clear drops at just 1mg a day, and recovered after stopping.
Some users believe S4 is less suppressive than RAD-140 or LGD-4033; that has never been measured. User blood work on S4 commonly shows lower LH, FSH and total testosterone by the end of a cycle, more so at higher doses. Suppression usually shows up as lower libido, weaker erections, fatigue and flat mood, and it reduces sperm production.
Blood work (testosterone, LH, FSH, estradiol, lipids and liver enzymes) is the only way to know how suppressed you are. A test 4 to 8 weeks after stopping shows whether levels are coming back.
Other Andarine Side Effects
Andarine’s safety in people has never been studied. These risks come from data on SARMs as a class and from user reports:
- Lower HDL cholesterol: a consistent finding across SARMs tested in people.
- Liver injury: published case reports describe drug-induced liver injury with SARM products, mostly LGD-4033, RAD-140 and ostarine. Andarine has not been studied for this and should not be assumed to be liver-safe.
- Heart and stroke risk: the FDA has warned that SARMs have been linked to a higher risk of heart attack and stroke.
- Hair loss and acne: possible through androgen activity in skin and hair follicles, particularly in men prone to male pattern baldness.
See also our guide to the long-term side effects of SARMs.
Andarine Cycle and Dosage: What Users Commonly Report
The doses below describe how S4 is commonly used, based on user reports. They are not clinical doses or recommendations. No study has tested andarine in healthy people at any dose.
| Reported Use | Daily Dose | What Users Commonly Report |
|---|---|---|
| Lower-dose cycles | 25mg or less | Fewer vision complaints; milder effects |
| Most commonly reported range | 25-50mg | 6 to 8 week cycles on a cut; vision changes in some users |
| Higher reported doses | Above 50mg | Vision changes reported most often; more suppression symptoms |
The daily amount is commonly split into two or three doses because S4 is assumed to have a short half-life. No human pharmacokinetic study has been published, so the half-life figures quoted online are not measured human values. Most reported cycles last 6 to 8 weeks, occasionally up to 12, and users report that vision changes and suppression build with higher doses and longer cycles.
S4 Before and After: Realistic Results
There are no controlled data on what andarine does to body composition in people, so every before-and-after is anecdotal. User logs commonly describe a leaner, harder look over 6 to 8 weeks and strength held during a diet; some claim several percentage points of body fat lost. These reports almost always come during a calorie deficit, are rarely measured with a DEXA scan, and rest on untested products. Why the photos are hard to read:
- Diet does most of the work: fat loss on a cut comes from the deficit. Holding muscle, andarine’s possible role, cannot be separated from training and protein in a photo.
- Photo conditions: lighting, a pump, a tan, water and carb manipulation and posing can change a physique more than any compound.
- Stacks and products: many logs combine S4 with other compounds, and an underdosed or mislabeled bottle changes the result.
Andarine for Cutting
Cutting is where S4 is mostly used, for keeping muscle in a calorie deficit. It restored muscle and reduced fat in castrated rats, but whether it does the same in dieting people has never been tested. Commonly reported cutting stacks add ostarine, which adds to the suppression and HDL drop, or cardarine (GW501516), which is not a SARM and was abandoned in drug development after it caused cancer in animal studies. Every extra compound also makes it harder to tell which one caused a problem, including a change in vision.
PCT After an Andarine Cycle
Post-cycle therapy (PCT) means taking a drug such as tamoxifen (Nolvadex) or clomiphene (Clomid) after a cycle to push the brain to restart LH and FSH output. Both are prescription drugs, neither is approved for this use, and no trial has tested PCT after a SARM cycle. Some S4 users run a short PCT; others wait for natural recovery. These are the protocols most commonly reported:
| PCT Drug | Commonly Reported Protocol | Duration |
|---|---|---|
| Tamoxifen (Nolvadex) | 20mg/day | 4 weeks |
| Clomiphene (Clomid) | 25-50mg/day | 4 weeks |
Without blood work, neither choice is an informed one. There is an extra catch after S4: clomiphene can itself cause visual symptoms such as blurring, spots or flashes, and its label advises stopping if they appear. A doctor can test hormones and treat persistent low testosterone properly. Read more in our guide to PCT for SARMs.
Andarine for Women
Andarine is often marketed as one of the best SARMs for women because it is considered mild. The evidence does not support that. Its only female data come from rats with their ovaries removed, and no woman has taken andarine in a published study. Andarine activates the androgen receptor, and androgens masculinize women. Commonly reported virilization signs include:
- A deeper or hoarse voice
- Facial and body hair growth
- Acne and oily skin
- Clitoral enlargement
- Irregular or missed periods
Voice changes and clitoral enlargement may not reverse after stopping. No dose has been shown to avoid these effects, and the vision side effects apply to women too. Our guide to SARMs for women covers the wider picture.
Andarine vs Ostarine, RAD-140 and LGD-4033
The biggest differences are how much human data exists and which risks stand out.
| Compound | Human Data | Commonly Reported Use | Stand-Out Risks |
|---|---|---|---|
| Andarine (S4) | None published; rat studies only | Cutting | Vision changes; suppression never measured in people |
| Ostarine (MK-2866) | Phase 2 and 3 trials at 1-3mg a day | Cutting; first cycles | Lower HDL and SHBG in trials; liver injury case reports |
| LGD-4033 (ligandrol) | Short phase 1 trial in healthy young men | Lean mass | Lowered testosterone, SHBG and HDL at 1mg a day; liver injury case reports |
| RAD-140 (testolone) | Phase 1 trial in women with advanced breast cancer | Bulking and strength | Strong suppression in user reports; liver injury case reports |
Andarine vs Ostarine: ostarine is the most studied SARM, with human trials showing modest lean mass gains at 1-3mg a day. Users often treat S4 as a step up on a cut, but “stronger” rests on user impressions, and S4 adds a vision risk ostarine is not known for.
Andarine vs RAD-140: RAD-140 is used for size and strength, and users generally report it as the more potent and more suppressive of the two. Neither has been tested in healthy people.
Andarine vs LGD-4033: LGD-4033 is better documented in people. Its short trial showed lean mass gains along with drops in testosterone and HDL, the clearest human evidence that even a low-dose SARM suppresses hormones.
Legal Status, Drug Testing and Product Quality
Andarine is not approved for human use anywhere. In the US it cannot legally be sold as a dietary supplement, which is why vendors label it “for research purposes only”. Rules differ by country; see are SARMs legal. WADA bans SARMs at all times and names andarine on its prohibited list.
Product quality is the other unknown. In a study published in JAMA, researchers analyzed 44 products sold online as SARMs. Only about half contained a SARM at all, and many contained other unapproved drugs or amounts that did not match the label. Independent batch testing shows what is in a bottle, but a certificate of analysis does not make a compound safe.
SARMs
Overview
- Form: Oral Capsules
- Research Dosage: 25–50 mg daily, split into morning/evening doses
- Typical Cycle: 6-8 weeks
- Cost: $65.95
- Stacking Options: Ostarine (MK-2866), Cardarine (GW-501516), SR9009
Pros
- Strong recomposition and cutting research profile
- Preserves lean mass during calorie deficits
- High-purity 25mg dosing format
Cons
- Possible vision-related side effects in some research subjects
- Testosterone suppression potential
- Not ideal for pure bulking phases
The Bottom Line
Andarine builds muscle, trims fat and protects bone in rats, but in people it is an untested compound with a distinctive vision side effect and suppression that should be expected.
- No human trial of andarine has been published; its doses, cycles and results come from user reports.
- Yellow-tinted vision and poor night vision are commonly reported, especially at higher doses, and long-term effects have never been studied.
- S4 should be expected to lower natural testosterone; blood work, not the “mild SARM” label, shows where you stand.
- Women face a risk of virilization that may be permanent, and no dose has been shown to be safe.
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