Why the math says once-weekly works for long esters, what the literature describes, and why the answer for any individual person still belongs with a clinician.
The most common scheduling debate among people on long-half-life injectable esters is also the least interesting: how often should I inject? The DoseCurve model has a clear mathematical answer, the clinical literature has a slightly more nuanced one, and the right answer for any individual person still belongs with a clinician who knows their bloodwork, their tolerability and their goals. This post walks through the math, the published evidence, and the gap between the two.
Nothing here is medical advice or a recommendation. It is background reading to inform a conversation with a prescriber.
For an ester with a half-life around 8 days (testosterone cypionate is the canonical example), the model behaviour is striking. Plot a once-weekly schedule and a twice-weekly schedule at the same total weekly milligrams and the chart shows:
The math is simple. A dose interval one half-life long lets each dose decay to half before the next arrives; that produces visible oscillation. A dose interval one-quarter of a half-life long lets each dose decay only ~16% before the next; the resulting line is nearly flat.
So from a "stability of serum levels" perspective, more frequent injections at smaller per-injection doses always produce a smoother curve at the same total weekly mass. The argument for more frequent dosing is purely a stability one.
The published clinical pharmacology on testosterone cypionate and enanthate, including the registration data for both intramuscular and subcutaneous formulations, supports the model: once-weekly dosing produces a meaningful peak/trough ratio, twice-weekly flattens it considerably, and longer intervals (every two weeks) produce wider oscillation. Endocrine Society guidance (2018) notes that injection frequency can be tuned to patient tolerability, with shorter intervals often producing more stable symptom control.
What the literature does not say:
The honest summary is: more frequent dosing is mathematically smoother, often subjectively preferred, and supported by clinical data as a viable option. It is not a clinical mandate.
Real cadence decisions are made on a wider basis than peak-to-trough ratio:
A "best" cadence balances all of these against the smoothness benefit the chart alone visualises.
Take a once-weekly schedule that's been in place for three months at 100 mg of cypionate. The chart shows steady-state peak around 195 mg, trough around 105 mg, average around 145 mg. The visible oscillation is real.
Switch the same total dose to 50 mg twice weekly. The chart shows steady-state peak around 165 mg, trough around 135 mg, average around 145 mg. Flatter, same average, half the per-injection dose.
Both schedules produce the same long-run exposure. The clinical question — which one matches your tolerability, your routine, your prescriber's monitoring plan, your symptom pattern — is not answered by the chart. It is answered by you and your clinician.
If you are considering a cadence change with a prescriber:
The model gives the conversation a visual anchor. It does not replace the conversation.
The pharmacokinetic argument for more frequent injections at the same total dose is straightforward. The clinical argument is more nuanced. Use the chart to see the shape change. Take the cadence decision to the person prescribing the medication.