Short answer: Propionate is a much shorter ester. Cypionate has a label half-life of about 8 days and is dosed every 1 to 4 weeks.1 Small human studies show propionate keeping testosterone up for only 1 to 2 days per injection,2 so it needs far more frequent shots. Cypionate is FDA approved; there is no marketed FDA-approved propionate product in the US.
| Testosterone cypionate | Testosterone propionate | |
|---|---|---|
| Mechanism | Long ester; slowly released from the oil depot, then cleaved to testosterone | Short ester; released and cleared much faster |
| Approval status | FDA approved (Depo-Testosterone and generics) | No marketed FDA-approved US product; earlier approvals are discontinued |
| Label dosing schedule | 50 to 400 mg into muscle every 2 to 4 weeks1 | No current US label |
| Half-life | about 8 days1 | Effective duration about 1 to 2 days: testosterone stayed above the lower normal limit for 1 day after 25 mg and 2 days after 50 mg2 |
| Time to peak (Tmax) | Not stated on the label | No measured Tmax; after 25 mg the ester was detectable from 3 to 36 hours3 |
| Dosing frequency | Every 1 to 4 weeks (label 2 to 4; guideline example weekly)4 | No label schedule; the short duration means much more frequent injections than cypionate |
| Strengths | 100 and 200 mg/mL1 | Commonly 100 mg/mL outside approved US products |
| Notable warnings | Raised hematocrit, blood pressure increases, BPH, VTE, abuse and dependence1 | Same testosterone class risks; no current US label |
The ester controls how fast testosterone leaves the oil at the injection site. A short ester like propionate is released quickly: in a 1976 study, testosterone stayed above the lower limit of normal for about 1 day after 25 mg and 2 days after 50 mg, compared with about 14 days after 250 mg of enanthate.2 A long ester like cypionate releases over about a week. That is why propionate is injected far more often to keep levels steady.
Not as a marketed product. Earlier US approvals are discontinued, so there is no current FDA label with dosing for propionate. Cypionate (Depo-Testosterone and generics) and enanthate are the approved injectable esters.1