- Ostarine (enobosarm, MK-2866) is the most studied SARM in humans, tested in over a dozen trials.
- At 3 mg a day, it increased lean mass by about 1.3 kg in older adults over three months.
- It still suppresses testosterone and lowers HDL, more so at the higher doses sold to bodybuilders.
- Ostarine is the SARM most often found in failed drug tests, sometimes from contaminated supplements.
Ostarine is usually described as the mildest SARM and the place to start. It does have more human research than any other SARM, which is worth something. This guide covers what that research shows, the risks, and what to know in Canada.
What is Ostarine?
Ostarine, also called enobosarm or MK-2866, was developed by GTx Inc. to prevent and treat muscle wasting, particularly in people with cancer. Large phase 3 trials in lung cancer patients didn’t meet their main goals for physical function, and it was never approved. It has since been studied for breast cancer and other conditions.
What human trials show
- In healthy older men and postmenopausal women, 3 mg a day for about three months increased lean body mass by roughly 1.3 kg and improved stair-climbing performance.
- In cancer patients, it increased lean mass compared with placebo.
- Side effects in trials were generally mild, but trials used low doses under supervision.
Side effects at real-world doses
Products sold for bodybuilding commonly contain 10 to 25 mg per dose, several times the studied amount.
- Testosterone suppression: dose-dependent; noticeable libido or mood changes after stopping are common at higher doses
- HDL cholesterol falls
- Liver enzymes can rise; liver injury has been reported with SARMs as a class
- Women: virilization is possible at higher doses
Drug testing
Ostarine is the SARM most frequently detected in anti-doping tests. Some athletes have tested positive after using contaminated supplements. It’s prohibited under the World Anti-Doping Code, enforced in Canada by the CCES.
Bloodwork
Check testosterone, LH, FSH, a lipid panel and liver enzymes before, during and after use through your family doctor or LifeLabs or Dynacare.
Legal status in Canada
Ostarine isn’t approved by Health Canada, and Health Canada has warned about unauthorized products containing SARMs. It isn’t listed in the Controlled Drugs and Substances Act.
Buying Ostarine in Canada
We stock MK-2866 Zionova, 10 mg tablets in bottles of 50. See the SARMs page for live prices and a cost-per-day calculator. Read our SARMs beginner’s guide and lab testing guide too.
Frequently asked questions
Is Ostarine the safest SARM?
It’s the most studied in humans, which makes its effects better understood, but it still suppresses testosterone and lowers HDL.
Does Ostarine need PCT?
At higher doses, suppression can be significant. Bloodwork after stopping shows whether recovery needs help.
How much muscle does Ostarine build?
About 1.3 kg of lean mass over three months at 3 mg a day in clinical research.
Is Ostarine legal in Canada?
It isn’t approved by Health Canada and isn’t listed in the CDSA.
Products mentioned in this guide
This article is general information for adults in Canada, not medical advice. Talk to a doctor or pharmacist before using any prescription drug, anabolic steroid or research compound, and get bloodwork done. If you’re in crisis, call or text 9-8-8 (Suicide Crisis Helpline) any time.
