Last updated: October 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 (ka = ln(2) / (0.25 × halfLife)). All injections in the cycle are summed to produce the accumulated blood level curve.
Compounds included
Includes 33 compounds across eight categories: testosterone esters (including enanthate and cypionate), anabolics (nandrolone, EQ, trenbolone, Masteron and Primo), orals (Anavar, Dianabol and Winstrol), support (HCG), GLP-1 medications (semaglutide, tirzepatide and retatrutide), healing peptides (BPC-157 and TB-500), growth peptides (CJC-1295, Ipamorelin, HGH and IGF-1 LR3), and other peptides (PT-141, Melanotan II and Pinealon).
Steady state and washout
Steady state is the point at which blood levels stabilise — a rough estimate of near steady state (~95%) is approximately 4.3 elimination half-lives after the first injection. For testosterone enanthate (half-life ~4.5 days), that is around day 19. Washout here means about 95% terminal elimination, approximately 4.3 half-lives after the final injection; it is not complete clearance.
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 (ka = ln(2)/(0.25 × halfLife)). 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, so the plotter still won't predict one from a dose alone. 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. If you enter your own measured total testosterone and the date it was drawn, the testosterone curve is rescaled to read in ng/dL for you, clearly labelled as your own draw rather than a predicted level.
When does testosterone reach steady state?
A rough estimate of near steady state (~95%) is approximately 4.3 elimination half-lives. For testosterone enanthate (half-life ~4.5 days), that is around day 19-20. For testosterone cypionate (half-life ~6 days), it is around day 26. Actual timing depends on the dosing schedule; the graph illustrates accumulation over time.
How long does testosterone stay in your system after the last injection?
Washout here means about 95% terminal elimination, approximately 4.3 half-lives after the last injection; it is not complete clearance. For testosterone enanthate (half-life ~4.5 days), this estimate is around 19–20 days after the final injection. For testosterone cypionate (half-life ~6 days), it is around 26 days. The graph illustrates the gradual decline after dosing stops.
What is the difference between testosterone enanthate and cypionate on the graph?
In the single-injection model, testosterone enanthate has a half-life of approximately 4.5 days and Tmax of about 3.0 days. Testosterone cypionate has a slightly longer half-life of approximately 6 days and Tmax of about 4.0 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