Short answer: in clinical trials, ostarine (MK-2866, enobosarm) was dosed at 1–3 mg a day for muscle (up to 30 mg a day for 14 days in a Phase 1 study, and 9–18 mg a day in breast cancer). On 3 mg a day for 86 days, older adults gained 1.3 kg more lean mass than placebo, while HDL fell 27% and total testosterone fell in men (Dalton 2011). Users commonly report 10–25 mg a day for 8 weeks; those doses have not been tested for muscle or safety.
Below: every studied dose, what users report for bulking, cutting and recomposition, and what is known about suppression at each level. Compound profile: ostarine fact sheet.
The best Ostarine dosage
There is no “best” dose from research, because ostarine was never tested for bodybuilding. The trial doses and results:
| Dose | Who and how long | Result | Source |
|---|---|---|---|
| 0.1–3 mg/day | 120 adults over 60, 86 days | 3 mg: lean mass +1.3 kg, fat −0.6 kg vs placebo; HDL −27%; ALT up in 5 of 24 | Dalton 2011 |
| 1 or 3 mg/day | 159 people with cancer, up to 113 days | Median lean mass +1.5 kg (1 mg), +1.0 kg (3 mg) | Dobs 2013 |
| 1–30 mg/day | Healthy and older men, 14 days (Phase 1) | SHBG and testosterone down with dose; ALT rise most common side effect | EMERALD protocol |
| 3 mg/day | ~650 lung cancer patients, 147 days (Phase 3) | Missed co-primary endpoints | POWER 1, GTx 2014 |
| 9 or 18 mg/day | 136 women with breast cancer | Grade 3/4 drug-related side effects in 8% and 16% | Palmieri 2024 |
| 3 or 6 mg/day + semaglutide | 168 adults over 60, 16 weeks | 71% less lean-mass loss (company data) | Veru 2025 |
| Dose studied | Who took part | Duration | What the study found | Source |
|---|---|---|---|---|
| 0.1, 0.3, 1 or 3 mg/day | Healthy men over 60 and postmenopausal women (n=120) | 86 days | Randomized, double-blind, placebo-controlled Phase 2 On 3 mg, lean mass rose 1.3 kg more than placebo; 1 mg gave +0.7 kg (not significant). Physical function and insulin resistance improved on 3 mg. HDL fell 17% (1 mg) and 27% (3 mg). | PubMed 2011 |
| 1 mg/day or 3 mg/day | Men over 45 and postmenopausal women with cancer and at least 2% weight loss (n=159) | Up to 113 days | Randomized, double-blind, placebo-controlled Phase 2 Median lean mass rose 1.5 kg (1 mg) and 1.0 kg (3 mg) from baseline; no change on placebo (100 people in the efficacy analysis). Serious adverse events were not judged drug-related. | PubMed 2013 |
| 1, 3, 10 or 30 mg/day | Healthy young men and elderly men with truncal obesity (Phase 1) | 14 days | Double-blind, placebo-controlled multiple-ascending-dose Phase 1 (G100402) Terminal half-life 14–21 hours. SHBG and total testosterone fell with dose; free testosterone did not change in a clinically significant way. A dose-dependent rise in ALT was the most common side effect. | isrctn.com 2021 |
| 3 mg/day | Patients with non-small cell lung cancer starting platinum + taxane chemotherapy (POWER 1) (n=321) | 147 days (primary analysis at day 84) | Randomized, double-blind, placebo-controlled Phase 3 Did not meet its co-primary endpoints. Stair-climb responders: 29.4% vs 24.2% on placebo. No lean-mass loss: 41.9% vs 30.4%. | clinicaltrials.gov 2014 |
| 3 mg/day | Patients with non-small cell lung cancer starting platinum + non-taxane chemotherapy (POWER 2) (n=330) | 147 days (primary analysis at day 84) | Randomized, double-blind, placebo-controlled Phase 3 Did not meet its co-primary endpoints. Stair-climb responders: 19.5% vs 24.8% on placebo. No lean-mass loss: 46.5% vs 37.9%. | clinicaltrials.gov 2014 |
| 9 mg/day or 18 mg/day | Postmenopausal women with AR+/ER+/HER2- advanced breast cancer (n=136) | Until progression (median follow-up 7.5 months) | Randomized, open-label Phase 2 (two doses, no placebo) Clinical benefit at 24 weeks in 32% (9 mg) and 29% (18 mg). Grade 3/4 drug-related side effects in 8% and 16%, most often raised liver enzymes. | PubMed 2024 |
| 3 mg/day or 6 mg/day, with semaglutide (Wegovy) | Adults over 60 with overweight or obesity on semaglutide (n=168) | 16 weeks | Randomized, double-blind, placebo-controlled Phase 2b (QUALITY) Company topline result: 71% less lean-mass loss than semaglutide alone (p=0.002) and 27% more fat loss (p=0.096). Total weight loss was similar. Not yet published in a journal. | ir.verupharma.com 2025 |
Sources: the studies linked in the table.
The user doses below come from the original article.
Bulking dosage + example cycle
Evidence level: anecdotal. The doses in this section are what users commonly report, kept from the original article. No trial tested them; they are several times the doses studied.
| Commonly reported | Ostarine |
|---|---|
| Weeks 1–8 (bulk) | 20 mg/day |
That is almost seven times the highest dose in the 86-day trial. The old claim that no PCT is needed at 20 mg has been removed: at just 1–3 mg a day, total testosterone fell by about 6–7 nmol/L in older men. For bulking, LGD-4033 is the SARM with more muscle data; see LGD-4033 dosage. Recovery: ostarine PCT.
Cutting dosage + example cycle
Evidence level: anecdotal. The doses in this section are what users commonly report, kept from the original article. No trial tested them; they are several times the doses studied.
| Commonly reported | Ostarine | Cardarine |
|---|---|---|
| Weeks 1–8 (cut) | 10 mg/day | 15 mg/day |
The newest trial is the most relevant to cutting: in adults losing weight on semaglutide, 3–6 mg a day of ostarine cut lean-mass loss by 71% over 16 weeks (company topline data, Veru 2025). Cardarine is often added for fat loss, but its fat-loss effect was never measured in people and its development stopped over animal cancer findings; see ostarine stacks and cardarine vs ostarine.
Body recomposition dosage + example cycle
Evidence level: anecdotal. The doses in this section are what users commonly report, kept from the original article. No trial tested them; they are several times the doses studied.
| Commonly reported | Ostarine | Cardarine |
|---|---|---|
| Weeks 1–8 (recomp) | 15 mg/day | 15 mg/day |
In the 86-day trial, 3 mg a day shifted body composition (more lean mass, less fat) without changing body weight, which is the closest the research comes to a “recomp” (Dalton 2011).
Safest Ostarine dosages
No dose has been shown to be free of side effects. The lowest doses with measured benefit (1–3 mg a day) already lowered HDL cholesterol and total testosterone, and ALT rose in some people on 3 mg (Dalton 2011). Higher doses raise exposure to all of these; at 9–18 mg a day in a cancer trial, serious drug-related side effects reached 8–16%, most often raised liver enzymes (Palmieri 2024). Several case reports describe cholestatic liver injury in young men using ostarine products (Mertens 2024).
The old claim that “studies use up to 15 mg a day and those doses are completely safe” was wrong: muscle trials used 1–3 mg, and safety at higher doses was not shown.
Dosages used in Studies and Human trials
See the table above. In short: 0.1–3 mg a day in the muscle-wasting trials (86–147 days), 1–30 mg a day for 14 days in Phase 1, 9–18 mg a day in breast cancer, and 3–6 mg a day with semaglutide. The half-life is about 14–24 hours, so trials used once-daily dosing (EMERALD protocol).
What dosage you should take
We can’t recommend a dose for an unapproved drug. What can be said: the doses with human data are 1–3 mg a day; users commonly report 10 mg for cutting and up to 20–25 mg for bulking, which is untested; and every measured side effect rose with dose. If you use it anyway, bloodwork before and after (testosterone, SHBG, HDL/LDL, ALT/AST) is the only way to see what it is doing; the PCT and bloodwork planner lists the markers. Products are often mislabeled, so the dose on the bottle may not be what you take (Van Wagoner 2017). How long to run it: ostarine cycle length.
Conclusion
Ostarine was studied at 1–3 mg a day for muscle, where it added about 1–1.5 kg of lean mass over 3–4 months and lowered HDL and testosterone. The 10–25 mg a day users report for cutting and bulking is several times higher and untested. Compare it with other SARMs in the SARMs database, and see real-world reports in ostarine before and after.
Frequently asked questions
What is the ostarine dosage used in studies?
0.1–3 mg a day for muscleEvidence: Trial
Muscle-wasting trials used 0.1–3 mg a day for 86–147 days. A 14-day Phase 1 study went up to 30 mg a day, and a breast cancer trial used 9 or 18 mg.
What is the best ostarine dosage for cutting?
Not tested for cuttingEvidence: Trial
No trial tested ostarine for cutting in healthy people; the 10 mg a day users report is untested. In older adults losing weight on semaglutide, 3–6 mg a day reduced lean-mass loss by 71% (company data).
Is 20 mg of ostarine too much?
Untested; far above trial dosesEvidence: Trial
It is almost seven times the highest dose in the main muscle trial, and its effects have not been studied. At 1–3 mg a day, HDL and total testosterone already fell.
What does 5 mg of ostarine do?
Not studied at 5 mgEvidence: Trial
No trial used exactly 5 mg for muscle. At 3 mg a day for 86 days, lean mass rose 1.3 kg vs placebo, HDL fell 27% and men's total testosterone fell.
Do you need PCT on ostarine?
Not establishedEvidence: Trial
At 1–3 mg in trials, total testosterone and SHBG fell but free testosterone, LH and FSH did not change significantly. Higher user doses have not been studied.
Should ostarine be split into two doses?
Trials dosed once dailyEvidence: Trial
Its half-life is about 14–24 hours, and trials used once-daily dosing.
Sources
- The selective androgen receptor modulator GTx-024 (enobosarm) improves lean body mass and physical function in healthy elderly men and postmenopausal women: results of a double-blind, placebo-controlled phase II trial
- Effects of enobosarm on muscle wasting and physical function in patients with cancer: a double-blind, randomised controlled phase 2 trial
- EMERALD study protocol (ISRCTN12213700, University of Liverpool, version 6.0, 2021): a window of opportunity study of enobosarm in ER+/AR+ early breast cancer
- ClinicalTrials.gov NCT01355484: Phase III Study of the Effect of GTx-024 on Muscle Wasting in Patients With Non-Small Cell Lung Cancer (POWER 1), posted results
- GTx, Inc. Provides Corporate Update And Reports 2013 Financial Results (press release, 4 March 2014)
- Activity and safety of enobosarm, a novel, oral, selective androgen receptor modulator, in androgen receptor-positive, oestrogen receptor-positive, and HER2-negative advanced breast cancer (Study G200802): a randomised, open-label, multicentre, multinational, parallel design, phase 2 trial
- Veru Announces Positive Topline Data from Phase 2b QUALITY Clinical Study: Enobosarm Preserved Lean Mass in Patients Receiving WEGOVY (Semaglutide) for Weight Reduction (press release, 27 January 2025)
- Liver Injury after Selective Androgen Receptor Modulator Intake: A Case Report and Review of the Literature
- Chemical Composition and Labeling of Substances Marketed as Selective Androgen Receptor Modulators and Sold via the Internet
