Ostarine (enobosarm, MK-2866)
MK2866, GTx-024, S-22
A non-steroidal SARM that reached late-stage clinical trials but was never approved; the most studied SARM, often seen as 'mild', which is not the same as harmless.
Legal status: Not approved anywhere and sold as a 'research chemical'; the FDA says SARMs cannot be legally sold as supplements, and possession rules vary by country.
What it gives
What people use it for and what the sources report. Strength is a general category from the literature: mild, clear or strong.
Purpose
Used to keep muscle on a diet and for 'recomp'. Studied in trials for cancer-related muscle wasting, breast cancer and muscle loss during GLP-1 weight loss; not approved for any use.
What people seek and what studies show
The most studied SARM, but only at doses far below sport use. In older men and postmenopausal women it added about 1.3 kg of lean mass, slightly reduced fat and improved stair-climbing power; in cancer-related wasting lean mass also rose. In two large trials in lung cancer it raised lean mass while missing its function endpoint — more mass did not mean more function. Healthy young athletes have never been studied.
Effects
Evidence: Limited human data — some human studies, small or short
Sought effects by goal (as reported)
Possible side effects
Possible does not mean certain: whether they appear depends on dose, duration, individual response and monitoring. Below — what to watch for and how to notice it early.
8 possible side effects
level · how often it is reportedWhat the levels mean
Level: general category from the literature, not your personal risk
How often
- common
- reported often
- possible
- reported in some people
- rare
- reported occasionally
How to lower the risks
For 6 of 8 possible side effects there are specific ways to lower the chance: everyday measures, supplements and options a doctor may consider. For the rest — general advice. No measure removes a risk completely.
Check hormones before and after; if they stay low, see an endocrinologist.
How each option helps (2)
- Regular blood tests — LH, FSH and testosterone show how deep suppression is and whether natural production has recovered afterwards.
- Working with a doctor — Assesses how deep suppression is and guides recovery afterwards, including fertility testing.
Avoid combining several oral steroids; regular cardio, soluble fiber (psyllium), less saturated fat and alcohol; if LDL/ApoB stay high, a doctor may consider a statin. Omega-3 only lowers triglycerides.
How each option helps (8)
- Regular blood tests — A lipid panel with ApoB shows how far HDL has dropped and LDL risen — changes you cannot feel.
- Working with a doctor — Interprets lipids and ApoB and decides whether a statin or other therapy is warranted.
- Avoiding alcohol and other liver stressors — Alcohol raises triglycerides; its small HDL bump does not lower heart risk.
- Regular cardio training — Raises HDL a little and lowers triglycerides; it cannot offset a steroid-driven fall in HDL on its own.
- Berberine — Placebo-controlled meta-analysis: LDL about 0.5 and triglycerides about 0.4 mmol/L lower; HDL unchanged. Trials are mostly small; no statin substitute.
- Citrus bergamot — Pooled small trials show lower LDL and triglycerides, but certainty is low to very low; it is no replacement for statins.
- Omega-3 (fish oil, EPA/DHA) — Clearly lowers triglycerides but does not fix the steroid HDL drop, the main lipid harm; DHA-containing oils may even raise LDL slightly.
- Psyllium husk fiber — Lowers LDL by about 0.2–0.3 mmol/L (roughly 5–10%), also on top of doctor-prescribed statins; no effect on HDL.
Products obtained without a prescription are often fake, mislabeled or non-sterile, and there is no way to check at home. For legal supplements, look for third-party testing (Informed Sport, NSF).
No alcohol, no other liver stressors, limit oral steroids and their combinations, check liver enzymes.
How each option helps (5)
- Avoiding alcohol and other liver stressors — Removes a major extra liver stressor during oral steroids and other hepatotoxic drugs.
- Regular blood tests — ALT, AST, GGT and bilirubin show liver strain before symptoms; heavy lifting alone raises AST/ALT for days, and GGT helps tell muscle from liver.
- Ademetionine (SAMe) — Used for intrahepatic cholestasis in some countries, but trials are small and of low quality; untested in steroid users. Stopping the oral steroid matters most.
- N-acetylcysteine (NAC) — Restores glutathione; proven in paracetamol poisoning and helped in early acute liver failure of other causes, but untested in steroid users.
- TUDCA (tauroursodeoxycholic acid) — Improves bile flow in cholestatic disease; in steroid cholestasis only case reports, with failures in severe cases. Stopping the oral steroid matters most.
What is unknown cannot be lowered, only avoided; tell your doctor what you have taken.
Stop at the first voice change and see a doctor — early stopping matters.
How each option helps (1)
- Working with a doctor — Steroid labels say to stop at the first mild signs (hoarse voice, facial hair, clitoral growth) to prevent permanent change; checks catch them early but do not make use safe.
Low-level side effects
How each option helps (3)
- Regular blood tests — A blood count shows hematocrit and hemoglobin climbing toward the range where clot and stroke risk rises.
- Therapeutic phlebotomy prescribed by a doctor — Only on a doctor's decision, never at a blood bank. Lowers hematocrit quickly but temporarily; repeated sessions drain iron, and a lower clot risk is unproven.
- Working with a doctor — Manages thick blood by changing what you use or, if justified, by therapeutic phlebotomy.
How each option helps (3)
- Adapalene — Reduces spots in many users. Redness, scaling, dryness and stinging are common early and usually ease; acne may look worse at first. Rarely, allergic swelling.
- Benzoyl peroxide — A first-line acne option. Dryness, redness and peeling are common at first; it bleaches hair and fabric; rarely, serious allergic reactions. Severe steroid acne needs a dermatologist.
- Zinc — Trials show a modest drop in inflamed spots, weaker than antibiotics; steroid acne is driven by androgens.
Check-ups and blood tests
Which tests and check-ups to do and when. This is a guide — agree the exact schedule with your doctor.
Which doctors can help
Get medical help at once if
- Yellow skin or eyes, dark urine, pale stools, intense itching, pain under the right ribs — see a doctor now; sudden severe abdominal pain with dizziness or fainting — call emergency services.
- Deepening voice, new facial hair, clitoral enlargement — stop and see a doctor: changes can become permanent. (women)
In an emergency, call your local emergency number.
For women
Women took low doses in trials without virilization, but sport doses are far higher: voice deepening, clitoral enlargement and body hair can appear and may not reverse. Must not be used in pregnancy.
Myth & fact
“Ostarine is so mild it doesn't suppress testosterone.”
Even low trial doses lowered total testosterone, SHBG and HDL, and biopsy-proven liver injury has been reported. Milder than RAD-140 is not the same as safe.
Combinations
No specific combination notes for this substance yet. The stack check still adds up side effects that several substances share.
Sources
Possible side effects by body system, combinations, how to lower the risks and which tests to do — free.
Open the stack check