Steady-state calculator
On a fixed dose and schedule, levels build before they level off. Put in the half-life and how often you dose, and see how far they build, how much they swing between doses, and how long until they plateau.
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Doses in published studies1
- weekly · Xyosted labelSource
Each is the dose a trial arm or a drug label states, linked to the text that states it. Who was studied, and how the dose was reached, are at the source.
Every 3.5 days: common TRT
Levels build to 2.40× a single dose at plateau.
Right after a dose
Right before next dose
Moderate swing
Peak and trough are amounts, so they wait for your dose. The swing is a ratio and doesn’t need one.
From your first dose.
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The link carries the numbers. Paste it in a thread and it opens filled in, no account needed.
peptidelabapp.com/calculator/steady-state?compound=test-e&unit=mg&every=84What sets the plateau
How long it takes to get there depends on the half-life alone: 90% of the way at about 3.3 half-lives, 99% at about 6.6, whatever the dose or the schedule. How high it builds depends on how much of each dose is still on board when the next one lands.
The swing is the peak divided by the trough. The same weekly amount split into more frequent injections narrows it; the average level stays where it was.
What the math assumes
The same dose on the same interval, every time, cleared at a constant rate. A missed dose or a schedule change restarts the approach to plateau. Half-lives are population averages, and individual variation is large.
Steady-state questions
- What is steady state?
- On a fixed dose and interval, each injection lands on top of what is left of the earlier ones, so levels climb for a while. Steady state is where they stop climbing: the amount cleared between injections equals the amount each injection adds, and every interval repeats the same peak and trough.
- How long does it take to reach steady state?
- It depends on the half-life alone, not on the dose or how often you inject: about 3.3 half-lives to reach 90%, 4.3 to reach 95%, and 6.6 to reach 99%. For an 8-day half-life that is roughly 27, 35 and 53 days.
- What is the accumulation factor?
- How many times higher the steady-state peak is than the peak after a single dose. It is 1 ÷ (1 − r), where r = 0.5^(interval ÷ half-life) is the fraction of each dose still on board when the next one lands. Short intervals against a long half-life build the most.
- What does the swing mean?
- The steady-state peak divided by the trough. Injecting the same weekly amount more often lowers it, which is why the calculator reads a high swing as big swings between doses; the average level is the same either way.
- Do I need to enter my dose?
- Not for accumulation, swing or time to plateau, which are ratios and times. Peak and trough are amounts, so they appear once you enter a dose. The calculator never fills one in for you. For compounds a published trial or a drug label gives a fixed dose, those doses and their schedules are listed with links to their sources, and one tap enters both.
- Does this give medical advice?
- No. It performs arithmetic on numbers you enter, assuming the same dose on the same interval every time. Missed doses or schedule changes restart the approach to plateau. For medical decisions, consult a qualified healthcare professional.
For informational purposes only. This tool performs mathematical calculations on numbers you enter and does not provide medical advice. Consult a healthcare professional for medical decisions. Steady-state math assumes consistent dose and interval; missed doses or schedule changes restart the accumulation clock. Pharmacokinetic half-lives are approximate population averages.