Reading bloodwork against your dose curve

How to compare lab results with the modelled curve — trough vs peak draws, timing, and what discrepancies usually mean.

A lab result on its own is a single dot. The DoseCurve chart is a line. The whole point of comparing the two is to figure out whether the line is in the right neighbourhood — and if it isn't, why not. This post walks through how to time a draw, where on the curve to expect the result, and the most common reasons measured and modelled values diverge.

Trough, peak, random — what each tells you

Trough is the value right before your next dose. It's the lowest point in the cycle and it answers the question "how low am I getting between shots?" Most clinicians anchor dose decisions to trough because it's the conservative reference — if your trough is in range, your peak almost certainly is too.

Peak is roughly where the curve tops out after a dose. For an intramuscular oil depot this can be hours to days post-injection depending on the ester. Peak draws answer "am I overshooting?" and matter most for compounds with a narrow therapeutic window.

Random draws — taken at no specific time relative to dosing — are nearly useless for protocol decisions. They produce a number, but without knowing where on the curve the number sits, you can't tell whether it's high, low, or exactly where it should be.

How draw timing is usually described

When and how blood is drawn is a decision for the ordering clinician. The conventions below are commonly cited in clinical pharmacology references and are included here as background only:

• Trough draw, weekly protocol: the morning of the next scheduled injection, before injecting.
• Trough draw, every-other-day protocol: immediately before the next dose.
• Peak draw, long ester (e.g. cypionate, enanthate): typically 24–72 hours post-injection; the modelled peak time on the chart corresponds to the half-life entered.
• Peak draw, short ester or peptide: hours post-injection.

Recording the exact time of the most recent dose on the lab requisition is standard practice so the result can be interpreted in context.

Reading the curve at the draw time

Hover over the chart at the date and time of your draw. The tooltip gives you the modelled total in milligrams at that point. That's your expected value in dose-equivalent terms. To compare it to a serum lab result you need to keep two things in mind:

1. Units differ. DoseCurve plots milligrams of compound in your system; serum labs report ng/dL, nmol/L, or pg/mL of the active hormone or analyte. The shapes should agree; the absolute numbers won't.
2. Conversion is individual. How many milligrams of testosterone cypionate in your system produces what serum reading depends on your body composition, SHBG, aromatisation, and assay choice. You're checking relative position on the curve, not absolute calibration.

If the chart says you're near trough and the lab says you're near the bottom of your reference range, the model and reality agree. If the chart says peak and the lab says trough, something is off.

Why model and reality diverge

Five common causes, roughly in order of frequency:

1. Draw timing wasn't what you think it was. Recheck the gap between your last injection and the actual blood draw. Lab waiting rooms add hours.
2. Your individual half-life isn't the textbook half-life. Published half-lives are population averages. Metabolism, body fat, and genetics shift the real value. If trough draws consistently come in lower than expected, your half-life may be shorter than the preset — edit it and the curve will refit.
3. Absorption was non-standard. Injection into scarred tissue, an oil that was cold, or a missed depot can change how much actually entered circulation. One off-day shouldn't trigger a protocol change.
4. Assay differences. LC-MS/MS, immunoassay and equilibrium dialysis don't always agree, especially at the extremes. Stick to one lab and one assay when comparing results over time.
5. Ester confusion. Mixed-ester products (e.g. blends) have multiple half-lives running in parallel. The DoseCurve preset for the dominant ester is an approximation, not a precise model.

When clinicians adjust protocols

One lab result is a data point, not a trend. Two consecutive draws taken at the same point in the cycle, on the same assay, with consistent timing, are what most clinicians treat as the threshold for considering a change. Any actual adjustment is a clinical decision — not something to make from the chart alone.

---

DoseCurve is an educational tool. Nothing on this site is medical advice. Always consult a qualified clinician before starting, changing or stopping any protocol.