What is the Y-axis?

The Y-axis shows relative blood-level concentration in arbitrary units proportional to your entered dose (mg or mcg). It is not an absolute serum testosterone value in ng/dL or nmol/L — actual blood levels depend on individual metabolism, injection site, body composition, and many other factors.

Think of the Y-axis as a shape indicator: it accurately shows you when levels peak, trough, and reach steady-state, even if the exact number doesn’t match a lab result.

What is the X-axis?

The X-axis is time in weeks from the start of your cycle. Week 0 is injection day 1. The chart extends 2 weeks past your selected cycle length so you can see the washout/clearance tail.

What does the curve shape mean?

• Rising phase (weeks 1–4 typically): Each injection adds more compound than has been cleared. Blood levels climb toward steady-state.
• Plateau / steady-state: The amount injected per interval equals the amount eliminated. The curve flattens into a saw-tooth wave — peaks right after each injection, troughs just before the next.
• Clearance tail (after last injection): No new compound is added; levels fall exponentially. The steeper the fall, the shorter the half-life.

Key pharmacokinetic terms explained

Half-life (t½)

The time it takes for blood concentration to fall to 50% of its current level. A compound with a 5-day half-life loses half its concentration every 5 days. Longer half-life = slower rise to steady-state, slower clearance.

Tmax

Time to peak concentration after a single injection. Testosterone Enanthate has a Tmax of ~2 days — so levels peak roughly 2 days after each shot, then decline.

Steady-state

Achieved after approximately 4–5 half-lives of continuous dosing. For Test E (t½ ~4.5 days), this is roughly 3–4 weeks. At steady-state, average levels stabilise between your trough and peak values.

Accumulation

With frequent dosing or long half-lives, each dose adds on top of residual levels from previous doses. This is why weekly Test E injections build up over several weeks rather than reaching full levels on day 1.

Trough

The lowest point in blood level, occurring just before your next injection. This is typically when side effects from low levels (low mood, libido) are felt, and when most bloodwork is done to measure stable trough levels.

Peak

The highest point after an injection. Occurs at Tmax. Large peak-to-trough swings (common with long esters dosed infrequently) can cause side effects at both ends.

Reading the metric cards

• Peak value: The maximum concentration your model predicts at any point in the cycle.
• Avg (steady-state): The average level during the middle 30% of your cycle — a rough estimate of your steady-state concentration.

Using the controls

• From / Through week: Lets you model kickstarters (short oral compounds in weeks 1–4), or compounds that are dropped mid-cycle. Each compound runs only between these weeks.
• Offset (days): Delays the first injection by this many days. Useful if you want Compound B to start mid-week relative to Compound A, or to model a front-load timing offset.
• Level adjustment slider (±100%): Scales a compound’s output up or down. Use it to model lower absorption (−20%), compare conservative vs. aggressive dosing, or represent bioavailability differences between individuals.
• Schedule: Injection frequency. More frequent injections (e.g. every other day for short esters) flatten peak-to-trough swings and are generally considered more stable. Less frequent injections create larger swings.

Why doesn’t my chart match my bloodwork?

This calculator uses published population-average pharmacokinetic values. Your actual levels depend on:

• Individual metabolism (faster or slower clearance)
• Injection depth and site (IM vs. subQ, glute vs. delt)
• Oil vehicle and concentration of the compound
• Body composition (body fat affects ester storage/release)
• The assay used by your lab (LC-MS/MS vs. immunoassay)

Use the Level adjustment slider to calibrate the model against your own bloodwork results. If your trough bloodwork reads ~20% lower than the chart shows, dial that compound to −20%.