Testosterone Cypionate Half-Life: How Long It Lasts, Steady State and Clearance
Testosterone cypionate half-life is quoted as eight days on the Depo-Testosterone label, and that single number explains most of what a man on TRT experiences: why a 200 mg shot feels strong in week one and flat in week two, why weekly dosing is steadier, why blood is drawn at six weeks and not two, and why the drug is still measurable a month after the last injection.
This article explains what the half-life means, where the eight-day figure comes from and why other sources say four to five days, how long one injection lasts, how long it takes repeated injections to reach a steady level, and how long the drug takes to clear after stopping. The facts come from the Depo-Testosterone label (Pfizer, revised September 2025), the Azmiro single-dose study (Azurity, 2025), a 2020 pharmacokinetic review and the Xyosted label for comparison.
What a Half-Life Is
A half-life is the time it takes for the amount of drug in the body to fall by half. For an oil-based ester injected into muscle it describes two steps at once: the ester leaving the oil depot and entering the blood, and the testosterone it releases being cleared. Free testosterone itself is cleared in minutes; the enanthate label puts its half-life at 10 to 100 minutes. The eight days belong to the depot.
That is why the number is stated as approximate. The rate at which oil leaves a muscle depends on the volume injected, the muscle, the oil, blood flow and body fat, so the same vial gives one man a slightly longer tail than another. The label's eight days is a population average, not a personal constant.
Where the Eight Days Come From, and Why Others Say Four
Half-life figures for testosterone esters by source
Depo-Testosterone label (2025)
Approximately 8 days
Not stated
Generic enanthate label
Not stated
Not stated; injections more often than every 2 weeks rarely indicated
2020 review, American Journal of Men's Health
About 4 days
About 4.5 days
Endocrine Society 2018 regimen
75 to 100 mg weekly or 150 to 200 mg every 2 weeks, same for both esters
Same
The gap between eight days and four is a matter of method and of what is being measured. The label figure describes the terminal decline of the whole curve, including the long shallow tail; the shorter figures describe how fast the clinically meaningful part of the level falls after the peak. Both are consistent with the same observed curve, in which a 200 mg dose is close to baseline by day 14. For dosing decisions the difference is irrelevant, which is why the guideline treats cypionate and enanthate as interchangeable; the comparison is on the cypionate vs enanthate page.
How Long One Injection Lasts
The Azmiro approval study measured the curve directly in 26 hypogonadal men given one 200 mg intramuscular injection:
- 1Mean peak: 758 ng/dL
- 2Time to peak: median about 72 hours, range 24 to 191 hours
- 3Decline: along the approximately eight-day half-life
- 4Near baseline: by day 14
In practical terms a single 200 mg injection keeps a hypogonadal man in the reference range for roughly ten days, with the first four at or near the top of it. That curve is drawn on the overview page; the one that matters more for a man on treatment is what happens when injections repeat.
Repeated Injections and Steady State
When the next dose arrives before the previous one has cleared, levels accumulate. With an eight-day half-life and a weekly interval, each injection adds to what is left of the last, and the total rises for about four to five half-lives before the amount added each week equals the amount cleared. That is steady state.
The chart is a schematic built from the label half-life and the Azmiro peak. Three things in it match clinical practice:
- 1The first weeks under-represent the final level. A man who feels little after his first injections of 100 mg weekly has not reached steady state; in the schematic the first peak is about 510 ng/dL and the fifth about 800.
- 2The peak-to-trough swing at steady state on weekly dosing is about 20 to 25%; on 200 mg every two weeks the level falls by more than half between the day-three peak and day fourteen, which is the "good week, flat week" men describe.
- 3The trough, measured just before an injection, is the stable number. The Endocrine Society guideline times the first blood draw mid-interval, and the Xyosted label, for the enanthate autoinjector, measures the trough after six weeks of weekly dosing, having found steady state by week six.
Splitting the weekly dose into two injections of 50 mg narrows the swing further at the cost of more injections; the choice between schedules is on the dosage page.
How Long It Takes to Clear
After the last injection the same half-life runs in reverse. From a steady-state level of about 800 ng/dL on weekly dosing:
Approximate decline after the last weekly injection (schematic, 8-day half-life)
1 week
About 55%
Little
2 weeks
About 30%
Energy and libido beginning to fall
3 weeks
About 17%
Levels near the low end of normal for many men
4 weeks
About 10%
Symptoms of the original deficiency return
6 weeks
About 3%
Essentially cleared; trace measurable by sensitive assays
Two cautions. The body's own production, suppressed during treatment, does not restart on this timetable; recovery of natural testosterone after stopping takes months and is not universal, which the side effects page covers under fertility and withdrawal. And drug testing does not follow blood levels: urine tests for the testosterone-to-epitestosterone ratio and for the ester itself can detect an injection for weeks beyond the point where blood levels have normalized.
Half-Life and Missed or Doubled Doses
The eight-day half-life is also why dosing errors are forgiving. A weekly injection taken two days late lowers the trough by a modest amount and the schedule simply continues; nothing resets. A doubled dose raises the next peak and the estrogen and hematocrit effects that follow it for a week or two, and the correction is to skip or reduce the next dose, not to add anything. Both situations are set out on the overdose page.
Half-Life at Higher Doses
In non-medical use the half-life does not change, but the arithmetic of accumulation does. At 500 mg a week the steady-state level is roughly five times the replacement curve, the peaks sit far above the reference range, and clearance after the last injection takes the same four to six weeks to fall by 95%, during which the suppressed natural production has not resumed. The numbers from the dose-response trials, and the blood work that tracks them, are on the bodybuilding page.
Frequently Asked Questions
Approximately eight days after intramuscular injection, per the Depo-Testosterone label. Published reviews using other methods give about four days; both describe a curve that returns to near baseline about two weeks after a 200 mg dose.
A single 200 mg injection peaks at about 72 hours (mean 758 ng/dL in the Azmiro study) and is near baseline by day 14; levels stay in the reference range for roughly ten days.
About four to five weeks of weekly dosing, which is why the first trough blood test is drawn at about six weeks.
Blood levels fall to about 10% of the treatment excess four weeks after the last injection and are essentially cleared by six weeks. Urine drug tests can detect the ester and the altered testosterone-to-epitestosterone ratio for longer.
No; the clearance rate is the same. A higher dose produces higher levels that take the same number of half-lives to fall, so the absolute amount remaining at any point is larger.
On a 200 mg biweekly schedule the level falls by roughly half between the day-three peak and day fourteen. Weekly or twice-weekly dosing of the same total keeps the swing to about 20 to 25%.
Cypionat.com is an independent educational resource. We are not affiliated with Pfizer, Azurity, Antares or any manufacturer, pharmacy or clinic. This content is for informational purposes only and does not constitute medical advice. Images on this site are illustrative artwork made for editorial purposes; they do not show real products, packaging or labels and are not an advertisement or an offer to sell.
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