When to take a SARM is really a question about half-life: how long a compound stays in circulation, and therefore how often it was given in the studies that tested it. The published trials almost all used a single daily dose, and the reason is pharmacokinetic rather than practical. This guide sets out the half-lives that have been measured, the ones that have only been estimated, and how the trial schedules were built around them. It is a reference for research design, not a usage guide.
Why half-life decides the schedule
A compound with a half-life near 24 hours reaches a steady concentration after four or five daily doses, and a single daily dose keeps that level fairly flat. A compound with a half-life of a few hours peaks and clears within the day, so a once daily schedule produces a sawtooth rather than a plateau. Trial designers choose the schedule that gives a stable exposure, which is why the human data for most SARMs comes from once daily protocols.
The measured half-lives
| Compound | Half-life | Source of the figure |
|---|---|---|
| Ostarine (MK-2866) | About 24 hours | Human phase I and II data (GTx) |
| Ligandrol (LGD-4033) | 24 to 36 hours | Human phase I (Basaria 2013) |
| Testolone (RAD-140) | About 60 hours (preclinical) | Rodent and primate data; no human figure |
| Ibutamoren (MK-677) | 4 to 6 hours, with GH effects lasting 24 hours | Human studies (Chapman 1996) |
| Cardarine (GW-501516) | Estimated 12 to 24 hours | Human phase I lipid studies |
| Stenabolic (SR-9009) | Under 4 hours (rodent) | Rodent pharmacokinetics; poor oral bioavailability |
| Andarine (S-4) | About 4 hours | Preclinical data |
| YK-11 and S-23 | Not established in humans | In vitro and rodent work only |
What the trial schedules looked like
The Ostarine phase II study gave the compound once daily for 12 weeks. The LGD-4033 study used once daily dosing for 21 days. The MK-677 studies that ran for a year or more also used a single daily dose, taken at bedtime in several of them because the growth hormone pulse it produces mirrors the natural night time release. Cardarine's human studies used once daily dosing over two to twelve weeks. None of the trials split the daily amount, and none tested whether food changed absorption in a meaningful way, although Ostarine's developers reported that it could be taken with or without a meal.
Short half-life compounds are the exception
Stenabolic and Andarine are the two where the pharmacokinetics argue against a single daily dose, and both have been discussed in the literature for that reason. SR-9009 in particular has such low oral bioavailability that the original researchers questioned whether meaningful blood levels are reachable by mouth at all. Andarine's short half-life is also linked to the visual disturbance reported in its early trials, which was worst at night and resolved when the compound cleared. Our guides on SR-9009 and S-4 go into both points.
Duration in the research
Trial lengths ranged from three weeks (LGD-4033 phase I) to twelve weeks (Ostarine phase II) and, for MK-677, up to two years. Longer exposure produced larger effects on lean mass but also larger changes in testosterone and HDL cholesterol, and the recovery period after the last dose was tracked for up to eight weeks. Our guide on post cycle therapy covers what those follow up samples showed.
What this means for research design
The practical summary from the published work is that a once daily schedule matches the half-life of Ostarine, Ligandrol, RAD-140, Cardarine and MK-677, that the two short half-life compounds have real pharmacokinetic limits, and that the newest compounds simply have no human timing data at all. If you are new to the topic, start with The ultimate guide to SARMs and First SARM cycle, then read the compound guide for whichever you are researching. All of our SARMs are batch tested, with certificates on the lab results page.
All products on this site are sold for laboratory research use only and are not for human consumption. Nothing in this article is medical advice or a dosing recommendation.