Short answer: It depends on the effect. A 2011 review of testosterone studies found that interest in sex rises after about 3 weeks and levels off by 6 weeks, mood and quality of life change within 3 to 6 weeks, fat and muscle change in 12 to 16 weeks, and bone changes show after about 6 months. Blood levels settle sooner: in the Xyosted study, testosterone reached steady state by week 6, which is why labs are timed weeks after a start or a dose change.
Saad and colleagues pulled together published studies of testosterone replacement to work out when each effect first appears and when it reaches its maximum. Their summary:
| Effect | First seen | Maximum or plateau |
|---|---|---|
| Interest in sex | About 3 weeks | Plateaus at 6 weeks |
| Erections and ejaculation | Varies | May take up to 6 months |
| Quality of life | 3 to 4 weeks | Takes longer |
| Depressed mood | 3 to 6 weeks | 18 to 30 weeks |
| Red blood cell production | About 3 months | 9 to 12 months |
| Blood lipids | About 4 weeks | 6 to 12 months |
| Insulin sensitivity | Within a few days | Blood sugar control shows at 3 to 12 months |
| Fat mass, lean mass, strength | 12 to 16 weeks | Stabilize at 6 to 12 months |
| Bone | About 6 months | Continues for at least 3 years |
| PSA and prostate volume | Small rise | Plateaus at 12 months |
The authors note wide variation between people and between products, likely tied to how each formulation releases testosterone. Treat these as ranges from studies, not a schedule your own body will follow.
The testosterone level in your blood stabilizes before most of the effects above show up. Long-acting esters build up over several doses until intake and clearance balance out, which is called steady state. The Depo-Testosterone label puts the half-life of injected cypionate at about eight days, and the Xyosted label says levels reached steady state by week 6 of weekly dosing. The steady-state guide works through the numbers for cypionate and enanthate.
Labels time lab checks around this. The Xyosted label says to measure the trough testosterone level (7 days after a dose) after 6 weeks of dosing and again 6 weeks after any dose change. The Endocrine Society guideline says men on testosterone should be monitored on a set plan during the first year, including symptoms, side effects, testosterone and hematocrit levels, and prostate cancer risk.
The same review puts the rise in red blood cell production at about 3 months, peaking at 9 to 12 months. That is the change behind the hematocrit checks in the labels: the Xyosted label asks for a hematocrit check before starting and about every 3 months on treatment. A normal reading in the first weeks does not mean it will stay normal later in the first year.
Effects on erections, mood and body composition depend on more than testosterone, which is part of why the review found such wide ranges. If something has not changed by the time the studies suggest it should, that is worth raising with your prescriber rather than changing the dose yourself.
Because effects arrive over weeks to months, memory is a poor guide. A simple log helps: note your dose and injection day, then once a week rate the things you started treatment for, such as energy, libido, mood and sleep, and record your lab results with their dates. Comparing week 2, week 6 and week 16 side by side shows the trend the studies describe, and gives your prescriber something concrete at the next visit. Dose Track keeps doses, lab results and a daily check-in together so the timeline is on one screen.
Read more on Dose Track: TRT steady state explained · TRT symptom tracker: what to log · Steady state (glossary) · Low testosterone · Half-life calculator · Xyosted dosing schedule