Testosterone cypionate is released slowly from the injection site, so each shot peaks a few days later and then fades over one to two weeks. The more often you inject, the flatter the curve. In this model, 100 mg a week as one shot swings about 300 ng/dL between peak and trough; the same 100 mg split into two shots swings about 90. A 200 mg shot every two weeks climbs past 1000 ng/dL and falls to roughly 380 before the next one. Levels take about four to five weeks to settle after you start or change a dose, which is why labs are drawn after that, not before.
Most men on testosterone replacement inject cypionate, and most of the questions that come up in the first months are about the curve: why the second week felt better than the fourth, whether 25 units is the same as 50 mg, and why the lab number looked nothing like what was expected. The chart above is a way to see the shape behind those questions. This page explains what it is showing, where it is reliable, and where only a lab can answer.
Why the schedule matters as much as the dose
Testosterone cypionate is testosterone with a fatty-acid tail attached, dissolved in oil. After an injection it sits in the muscle or fat and leaks into the blood as the ester is cleaved off. That slow release is the whole point of the ester, and it also sets the shape of the curve. The FDA label lists a half-life of about eight days for cypionate given into muscle; kinetic studies of the enanthate and cypionate esters, including the Schulte-Beerbühl and Nieschlag comparison cited below, put the effective figure closer to four to five days, with the peak arriving two to four days after the shot. A single injection is mostly gone in two weeks either way.
That is why the interval changes so much. Inject 200 mg every two weeks, the schedule on the original label, and the level overshoots the normal range for several days, then slides back down toward where it started. Inject the same total as 100 mg every week and the peak drops and the trough rises. Split it again into 50 mg twice a week and the curve is nearly flat. The table shows the model's steady-state numbers for 100 mg a week delivered six different ways.
| Schedule (100 mg a week total) | Per injection | Peak | Trough | Swing |
|---|---|---|---|---|
| Every day | 14 mg | 800 | 790 | about 10 |
| Every other day | 29 mg | 810 | 780 | about 30 |
| Twice a week | 50 mg | 830 | 740 | about 90 |
| Once a week | 100 mg | 910 | 615 | about 300 |
| Every 10 days | 143 mg | 1015 | 505 | about 510 |
| Every 2 weeks | 200 mg | 1180 | 380 | about 800 |
Guidelines have moved with this. The Endocrine Society's 2018 guideline lists 75 to 100 mg weekly or 150 to 200 mg every two weeks for cypionate and enanthate, and notes that the two-week schedule produces high peaks and low troughs that some men feel as swings in energy, mood, and libido. The AUA guideline suggests aiming for the middle of the normal range, roughly 450 to 600 ng/dL. Neither guideline requires twice-weekly dosing, and plenty of men do well on a weekly shot. The flatter curve is a reason to shorten the interval if the swings bother you or if a level comes back high, and the extra injections are the cost.
Reading the chart against a lab result
The chart's most useful lesson is that "your testosterone level" on injections is not one number. On a weekly shot the model puts day two around 900 ng/dL and day seven around 615. A lab drawn on either day is correct; they are just different points on the same curve. Before you compare a result with the chart, or with a previous result, check when the blood was drawn relative to your last injection.
For cypionate and enanthate, the Endocrine Society guideline suggests measuring midway between injections. Many clinicians instead order a trough, drawn the morning of your next shot before you take it, because it shows the lowest point you reach and is easy to time consistently. Either is fine as long as it is the same each time. The draw should wait until the curve has settled, which in the model takes about four to five weeks; the Xyosted label reports steady state by week six for weekly enanthate. A level in week one or two mostly measures how far you have climbed, not where you will land.
Then expect the real number to differ from the estimate, sometimes by a lot. The model scales dose to level using averages from clinical studies, and the spread around those averages is wide. In the McFarland and Spratt study of weekly subcutaneous cypionate, patients on similar doses ranged from about 200 to 1400 ng/dL between injections. Body weight, body fat, SHBG, clearance rate, injection depth, how much testosterone your own testes still make, and the lab's assay all move the number. The chart tells you the shape and the direction a change will push you. The lab tells you the value.
Units, milligrams, and milliliters
Most men draw cypionate with an insulin syringe, which is marked in units. A unit is a volume, one hundredth of a milliliter, so 100 units is 1 mL and 25 units is 0.25 mL. How much testosterone that holds depends entirely on the vial. The common 200 mg/mL strength gives 50 mg in 25 units; a 100 mg/mL vial gives 25 mg in the same syringe fill. If your pharmacy switches strengths, the units on your instructions change even though the milligrams do not, which is the single most common way doses go wrong at home. The calculator converts either direction, and the summary line always shows all three: units, milliliters, and milligrams.
Cypionate is labeled for deep intramuscular injection, and many clinicians now also prescribe it subcutaneously, into belly or thigh fat, with a smaller needle. The McFarland and Spratt data suggest weekly subcutaneous cypionate holds levels steady between shots, and Xyosted, a subcutaneous enanthate autoinjector, is FDA-approved on a weekly schedule. The model here does not distinguish the two routes. Our guide to intramuscular versus subcutaneous injections covers technique, needle sizes, and what to expect from each.
Do not change your dose or schedule based on this chart. Talk with the clinician who prescribes your testosterone before adjusting anything, and seek care promptly if you notice:
- Chest pain, shortness of breath, or a sudden severe headache
- Weakness or numbness on one side, trouble speaking, or vision loss
- Painful swelling in one leg, which can signal a clot
- A hematocrit result above 54 percent, or symptoms like headache, flushing, and dizziness that can go with thick blood
- Marked mood changes, aggression, or new sleep apnea symptoms such as loud snoring and daytime exhaustion
- Breast tenderness or swelling that is new or getting worse
Testosterone is a controlled substance. Use only what is prescribed to you, never share vials or needles, and dispose of sharps in a proper container.
How this calculator works
The page runs a standard one-compartment pharmacokinetic model in your browser. Each injection is treated as a depot that releases testosterone with a first-order half-life of six days, between the FDA label's eight-day figure and the four to five days seen in kinetic studies of the cypionate and enanthate esters. A faster one-day process shapes the rise, which puts the peak of a single shot about three days after injection, matching the two to four days reported in those studies. Every injection in the eight-week window is stacked on top of the ones before it, so the curve climbs for the first weeks and then repeats. Steady-state peak, trough, average, and swing are read from the last full cycle. The scale from milligrams to ng/dL is set so that 75 mg a week averages about 600 ng/dL, in line with the Xyosted label's steady-state average of 553 ng/dL on weekly enanthate and the 627 ng/dL mean in the McFarland and Spratt subcutaneous cypionate study.
The model assumes complete absorption, no difference between intramuscular and subcutaneous injection, no remaining natural production, and average clearance. It ignores body weight, SHBG, and individual variation, all of which can shift real levels by hundreds of ng/dL. It is built for adult men on testosterone cypionate or enanthate at replacement doses and does not apply to other esters, gels, pellets, or undecanoate. Nothing you enter is transmitted or stored. If you are wondering whether your symptoms point to low testosterone in the first place, the low testosterone calculator is the place to start, and the treatment options guide compares injections with the alternatives.
Common questions
It depends on the vial. Insulin-syringe units measure volume, and 100 units equal 1 mL. With the common 200 mg/mL strength, 25 units is 0.25 mL, which is 50 mg. With a 100 mg/mL vial, the same 25 units is only 25 mg. Always check the concentration printed on your vial before converting, and confirm any change with the clinician who prescribes it.
The chart is a calculated estimate built on average absorption and clearance rates. Real levels depend on your body weight and fat mass, your SHBG, how fast you clear testosterone, whether the injection went into muscle or fat, how much testosterone your own body still makes, the assay the lab uses, and the exact hour of the draw. Two people on the same protocol can land hundreds of ng/dL apart. Your measured level is the number that matters, and your clinician adjusts the dose to that, not to a model.
Splitting the same weekly dose into two injections roughly cuts the swing between peak and trough by two thirds in the model. A flatter curve tends to mean steadier energy, mood, and libido, and less time above the range, which the Endocrine Society and AUA both flag as a reason to shorten the interval or lower the dose. The trade is more injections. Many men do well on weekly shots, and the right schedule is the one you will keep up with consistently.
Each injection stacks on what is left of the last ones, so levels climb for the first few weeks before they settle into a repeating pattern. With cypionate that takes roughly four to five weeks in the model, and the Xyosted label reports steady state by week six for weekly enanthate. That is why a level drawn in week one or two says little about where your dose will end up, and why most clinicians wait several weeks after any change before rechecking.
For cypionate and enanthate injections, the Endocrine Society guideline suggests measuring midway between injections, once levels have settled. Some clinicians prefer a trough, drawn just before your next shot, because it shows the lowest point you reach. Either way, note the timing relative to your last injection on the lab order, because the same dose can read very differently on day one and day seven. Your clinician will tell you which they want.
- FDA (DailyMed, National Library of Medicine). DEPO-TESTOSTERONE (testosterone cypionate injection) prescribing information: clinical pharmacology, dosage and administration (2024)
- Endocrine Society (Bhasin S, et al.), Journal of Clinical Endocrinology and Metabolism. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline (2018)
- American Urological Association (Mulhall JP, et al.), Journal of Urology. Evaluation and Management of Testosterone Deficiency: AUA Guideline (2018)
- Schulte-Beerbühl M, Nieschlag E, Fertility and Sterility. Comparison of testosterone, dihydrotestosterone, luteinizing hormone, and follicle-stimulating hormone in serum after injection of testosterone enanthate or testosterone cypionate (1980)
- McFarland J, Craig W, Clarke NJ, Spratt DI, Journal of the Endocrine Society. Serum Testosterone Concentrations Remain Stable Between Injections in Patients Receiving Subcutaneous Testosterone (2017)
- FDA (DailyMed, National Library of Medicine). XYOSTED (testosterone enanthate injection) prescribing information: clinical pharmacology, steady-state concentrations by weekly dose (2025)
- MedlinePlus (NIH). Testosterone Injection: Drug Information