Steady State and How Long Before A Compound Takes Effect?
Conclusion: Half-lifes are important here, and it's 5 half-lifes before the compound is at a stable level. For a compound with a half-life of 24 hours, that's 5 days. Before this, the compound will not be at its full effect on the body. Speed of results and side effects will depend on how the compound itself works. Getting to steady state is necessary to most efficiently utilize the compound.
A common question or statement in /r/PEDs is 'Guys, I am on day 2 of LGD and I am feeling great!', or 'I've been on for 3 days, how long until I notice anything?'. These two opposite extremes are understable questions from new and experienced PED users alike.
The rule of thumb is that 5 half-lifes will achieve a steady state in the subject. If your compounds half life is 24 hours, that would be 5 days. If your compounds half life is 36 hours, the steady state would take 7.5 days. And the promised results (and side effects) will follow this time. This could be expressed in a formula as:
'Steady State' = 5 x (length of half life in days).
For LGD, let's take the half-life as 36 hours. That would be:
5 x 1.5 = 7.5 days
For Ostarine and LGD, this is an easy calculation. But what about something with a short half-life like SR9009 or RAD140? For both of these compounds, to achieve steady state as quickly as possible you will want to take the recommended dose split multiple times per day. The plus side is that it's much quicker to reach steady state. SR9009 has a half life of ~4 hours, so assuming you're dosing every 4 hours, the math would be
5 x 0.16 = 0.8 days
In reality, ain't nobody got time to wake up in the middle of the night to take a SARM, so will be closer to 2 days.
The time to reach steady state is defined by the elimination half-life of the drug. After 1 half-life, you will have reached 50% of steady state. After 2 half-lives, you will have reached 75% of steady state, and after 3 half-lives you will have reached 87.5% of steady state. The rule of thumb is that steady state will be achieved after 5 half-lives (97% of steady state achieved). https://www.certara.com/2013/11/25/understanding-steady-state-pharmacokinetics/?
For a drug with a longer half-life, of say 6 days like Nolva, it's possible to front load the dose. That would be 20mg per day, instead of 10mg per day. So instead of (5 x 6 days) 30 days to reach steady state, you're reaching it in half that time of 15 days, at which point you can drop the dose to maintenance of 10mg per day.