Human trials of SARMs were short: three weeks for LGD-4033 and about three to four months for ostarine. Nothing is known about longer use in people. What trials do show is that suppression of testosterone and drops in HDL cholesterol build up with dose and time.
- Longer use means deeper suppression and a longer recovery.
- HDL usually falls within the first few weeks.
- Bloodwork before, during and after is the best guide.
“How long should I run it?” is one of the most common SARM questions. There is no approved answer, because no SARM is an approved medicine. What we can do is look at how long they were given in clinical trials, what changed over that time, and what that means for anyone considering them.
How long the trials lasted
| SARM | Trial length | Studied amount | Main findings |
|---|---|---|---|
| Ostarine (enobosarm) | 12 weeks to about 4 months | 1–3 mg a day | About 1–1.5 kg lean mass; HDL and testosterone fell |
| LGD-4033 (ligandrol) | 21 days | 0.1–1 mg a day | About 1.2 kg lean mass at 1 mg; dose-dependent HDL drop and suppression |
| RAD-140 (testolone) | Early cancer trials only | Not applicable | Limited human data; liver injury case reports |
| S4 (andarine) | No published efficacy trials in people | Not applicable | Vision changes reported by users |
These durations tell us the time frames where human data exists, not a recommendation. Beyond them, there is simply no information.
What builds up with time
Suppression
SARMs reduce LH and FSH, the pituitary signals that tell the testes to make testosterone and sperm. In trials, testosterone fell within weeks and the drop grew with dose. Longer suppression generally means a longer wait for natural production to recover. See recovery after SARMs.
Cholesterol
HDL fell noticeably within the first few weeks in both the ostarine and LGD-4033 trials. In the LGD trial, HDL dropped by roughly a fifth at the highest dose in just three weeks. Over months, a sustained low HDL adds to cardiovascular risk.
Liver
Liver injury reported with SARMs has generally appeared after several weeks of use, often at amounts well above trial doses.
Why more is not better
In the trials, the extra lean mass from higher doses was small while side effects rose clearly. LGD-4033 at 1 mg added about 1.2 kg over three weeks; amounts discussed online are often 5–10 times higher, with no human data on what that does. Longer, higher use mainly adds suppression and lipid changes.
Signs it is time to stop
- Liver enzymes several times above normal, or any jaundice, dark urine or itching
- HDL that has fallen to very low levels
- Low libido, erectile problems, low mood or fatigue from suppression
- Vision changes (especially with S4)
- Headaches, raised blood pressure or new acne
Breaks between uses
Because there are no long-term human studies, a cautious approach is to treat any period of SARM use as something your body needs to recover from fully before considering it again. Practically, that means waiting until testosterone, LH and FSH are back to your baseline on bloodwork and HDL cholesterol has returned to its normal range. For many people this takes at least as long as the period of use, and sometimes longer. Repeated back-to-back use keeps hormones suppressed and HDL low for long stretches, which is exactly the situation where the unknown long-term risks matter most.
Bloodwork timing
- Baseline: testosterone, LH, FSH, lipid panel, liver enzymes, complete blood count.
- Three to four weeks in: lipids and liver enzymes, the earliest to change.
- After stopping: testosterone, LH and FSH at about four to eight weeks to confirm recovery.
Your family doctor can order these, or you can pay privately at LifeLabs or Dynacare. See our bloodwork guide.
The bigger picture
Most people looking at SARMs want visible progress in a few months. Trial data suggests modest lean mass gains that are in the same range as a few months of well-structured training and enough protein for a newer lifter. Getting training, food and sleep right first often delivers more than any SARM. See ostarine research, SARMs 101 and SARMs vs steroids.
Legal status
SARMs are not authorised by Health Canada for human use and are sold for research. All are banned in sport by the World Anti-Doping Agency.
Frequently asked questions
How long were SARMs tested in humans?
Ostarine for about three to four months and LGD-4033 for 21 days in the published trials. There is no human data on longer use.
Does longer SARM use cause more suppression?
Trials showed suppression increases with dose, and longer suppression generally means a longer recovery.
When should I get bloodwork on SARMs?
Before starting, three to four weeks in, and four to eight weeks after stopping to confirm recovery.
Photo: Ales Krivec, StockSnap (public domain).
General information about research compounds, not medical advice. SARMs are not approved for human use in Canada.
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