You can start testosterone therapy once you have two morning blood tests showing total testosterone below 300 ng/dL, along with symptoms of deficiency and no medical conditions that would make treatment unsafe. The process typically takes a few weeks from your first appointment to your first dose, since it requires lab work, a symptom evaluation, and sometimes additional screening depending on your age and health history.
The Blood Test Requirement
A single low reading isn’t enough. Testosterone levels fluctuate throughout the day and from one day to the next, so the FDA requires at least two documented low serum testosterone levels before treatment can begin. Both draws need to happen in the early morning, ideally between 8 and 10 AM, when testosterone peaks. If your first test comes back below 300 ng/dL (the threshold recommended by the American Urological Association), you’ll need to repeat it on a separate day to confirm.
If both results fall below 300 ng/dL and you have symptoms consistent with low testosterone, you meet the basic diagnostic criteria. Symptoms alone aren’t sufficient, and low numbers alone aren’t sufficient either. You need both.
Symptoms That Qualify
Low testosterone produces a recognizable cluster of problems that overlap with normal aging, which is part of what makes diagnosis tricky. The symptoms doctors look for include reduced sex drive, erectile difficulties, fatigue, loss of muscle mass, increased body fat, decreased bone density, mood changes, and cognitive fog. Screening questionnaires used in clinical settings ask about all ten of these areas, scoring severity on a scale to help distinguish genuine deficiency from mild age-related changes.
One important distinction: the FDA has not approved testosterone products for men whose only issue is low levels due to aging. There needs to be an associated medical condition driving the deficiency, such as a problem with the testes, pituitary gland, or hypothalamus.
Baseline Lab Work Before You Start
Beyond the two testosterone draws, your doctor will order several other tests before writing a prescription. These serve two purposes: ruling out conditions that make testosterone unsafe and establishing baseline values for monitoring later.
- Hematocrit: This measures the percentage of red blood cells in your blood. Testosterone stimulates red blood cell production, so if your hematocrit is already elevated, treatment could push it into a dangerous range and increase clotting risk.
- PSA (men over 40): Prostate-specific antigen screening is recommended before starting treatment. A PSA above 4 ng/mL, or above 3 ng/mL in men at high risk for prostate cancer, requires a urology evaluation before testosterone can begin.
- LH level: Luteinizing hormone helps determine whether the problem originates in the testes (primary hypogonadism) or in the brain’s signaling system (secondary hypogonadism). This distinction matters because secondary hypogonadism with very low testosterone (below roughly 175 ng/dL) and low LH may signal a pituitary tumor or other structural problem that needs an MRI before treatment starts.
- Prolactin: Elevated prolactin combined with low testosterone and low LH can indicate a pituitary lesion called a prolactinoma, which would need to be addressed on its own terms rather than simply masked with testosterone.
If all your labs come back within acceptable ranges and your imaging (if needed) is clear, you’re medically eligible to begin.
Conditions That Delay or Prevent Treatment
Several health situations will stop a doctor from prescribing testosterone, either temporarily or permanently. Active breast or prostate cancer is an absolute contraindication. So is a palpable prostate nodule that hasn’t been evaluated. If you’ve had a heart attack or stroke within the last six months, you’ll need to wait. Untreated severe sleep apnea, uncontrolled heart failure, and blood clotting disorders also rule out treatment until those conditions are managed.
Planning to have children is another major consideration. Testosterone therapy suppresses sperm production, sometimes to zero. If you want to conceive within the next six months, standard practice is to avoid testosterone entirely and use alternative treatments that raise your levels without shutting down fertility. If pregnancy is 6 to 12 months out, some protocols allow testosterone alongside fertility-preserving medications. Either way, a baseline semen analysis is recommended for any man who wants to keep his options open.
Age Considerations
There is no single minimum age for testosterone therapy. In adults, the determining factor is your lab values and symptoms, not your birthday. Men in their 20s and 30s with confirmed hypogonadism from a medical cause can qualify just as readily as men in their 50s and 60s.
For adolescents, testosterone may be prescribed for delayed puberty or specific endocrine conditions, but these situations are managed by pediatric endocrinologists and follow different protocols than adult testosterone replacement. The evaluation is more cautious because testosterone affects bone growth plates and long-term development.
At the other end of the age spectrum, age-related testosterone decline alone is not an FDA-approved indication for treatment. A 65-year-old whose testosterone has gradually drifted below 300 ng/dL still needs an identifiable associated medical condition to qualify.
How Quickly You’ll Notice Changes
Once you actually begin treatment, improvements don’t arrive all at once. They follow a fairly predictable timeline. Sex drive is one of the first things to respond, with noticeable changes starting around three weeks and reaching a plateau by six weeks. Fatigue and low energy tend to improve within the first four to six weeks. Quality of life and mood follow a similar track, with initial gains at three to four weeks and continued improvement over the following months.
Body composition changes take longer. Reductions in fat mass and gains in lean muscle begin around 12 to 16 weeks, stabilize between 6 and 12 months, and can continue making marginal improvements over years. If you’re starting testosterone hoping to feel more energetic and interested in sex, you’ll likely notice something within the first month. If your primary goal is physical changes, plan on giving it at least three to four months before judging whether it’s working.
The Realistic Timeline From First Visit to First Dose
Putting it all together, here’s what the process typically looks like. At your first appointment, your doctor orders morning bloodwork. You return for a second draw on a different day to confirm. If additional screening like an MRI is needed, that adds another week or two. Once your results are reviewed and you’ve discussed the risks, benefits, and your fertility plans, a prescription can be written. For most men, this means two to four weeks from the initial visit to starting treatment, assuming no complications arise in the workup.