Last updated: May 2026
Steroid Cycle Plotter — Injectable Blood Level Graph
See your blood levels before you inject. The InjectBuddy cycle plotter graphs how injectable steroid and Testosterone (TRT) levels rise and fall across a full cycle: pick a compound, enter your dose and injection frequency, and the curve updates instantly to show your peaks and troughs, time to steady state, and washout period — all from a real pharmacokinetic (PK) model.
How the PK model works
The plotter uses a one-compartment model with first-order absorption and elimination. Each injection is modelled independently using the formula C(t) = dose × ka/(ka − ke) × (e−ke×t − e−ka×t), where ke is the elimination rate constant (derived from half-life: ke = ln(2) / halfLife) and ka is the absorption rate constant (solved numerically from Tmax using a bisection algorithm). All injections in the cycle are summed to produce the accumulated blood level curve.
Compounds included
Includes 21 compounds across seven categories: testosterone esters (propionate, enanthate, cypionate, undecanoate, sustanon), nandrolone esters (NPP, Deca), anabolics (EQ, Masteron), GLP-1 medications (semaglutide, tirzepatide, retatrutide), healing peptides (BPC-157, TB-500), growth peptides (CJC-1295, Ipamorelin, HGH, IGF-1 LR3), and support compounds (HCG).
Steady state and washout
Steady state is the point at which blood levels stabilise — this occurs at approximately 4.3 half-lives after the first injection. For testosterone enanthate (half-life ~4.5 days), steady state is reached around day 19. Washout — the point at which levels drop to ~1% of peak — is approximately 4.3 half-lives after the final injection.
Frequently asked questions
How does the cycle plotter calculate blood levels?
The plotter uses a one-compartment pharmacokinetic model with first-order absorption and elimination. For each injection, the serum concentration is modelled as: C(t) = dose × ka/(ka − ke) × (e−ke×t − e−ka×t), where ke is the elimination rate constant derived from half-life (ke = ln(2)/halfLife) and ka is the absorption rate constant. All injections are summed to give the total blood level at any point in time.
Why does the plotter use relative units instead of ng/dL?
Absolute serum concentrations (in ng/dL) require compound-specific pharmacokinetic parameters including volume of distribution and bioavailability that are not reliably available for all compounds. The relative units shown are directly proportional to your dose and allow you to compare peak-to-trough ratios, evaluate injection frequency, and estimate steady-state timing accurately.
When does testosterone reach steady state?
Steady state is reached after approximately 4.3 half-lives. For testosterone enanthate (half-life ~4.5 days), that is around day 19–20. For testosterone cypionate (half-life ~5 days), it is around day 21–22. The cycle plotter shows the exact steady-state day for whichever compound you select.
How long does testosterone stay in your system after the last injection?
The washout period (time to drop to roughly 1% of peak) is approximately 4.3 half-lives after the last injection. For testosterone enanthate (half-life ~4.5 days), washout is around 19 days after the final injection. For testosterone cypionate (~5 days), it is around 21 days.
What is the difference between testosterone enanthate and cypionate on the graph?
Testosterone enanthate has a half-life of approximately 4.5 days and Tmax of about 2 days. Testosterone cypionate has a slightly longer half-life of approximately 5 days and Tmax of about 2.5 days. The two esters produce nearly identical blood level curves at the same dose and frequency. For practical Testosterone (TRT) purposes, they are interchangeable.
Related guides
Other Testosterone (TRT) & injectable calculators
References
The pharmacokinetic basis for this model (first-order depot absorption and elimination, ester half-lives). Estimates use published half-lives in a simplified model — individual results vary; not medical advice.
- Flip-flop pharmacokinetics: depot release governs the decline curve — Ther Deliv, 2011
- Allometric scaling of testosterone enanthate PK (one-compartment, first-order model) — J Endocr Soc, 2023
- Intramuscular testosterone undecanoate: phase I pharmacokinetics (ester half-lives) — Eur J Endocrinol, 1999
- Pharmacology of testosterone replacement therapy preparations — Transl Androl Urol, 2016