A man who has been on TRT for months but is still tired, has noticed no real change in libido or strength, or still feels mentally flat has a reasonable complaint. It’s rarely evidence that testosterone replacement doesn’t work for him, though. In practice, “TRT not working” most often comes down to one of a handful of checkable variables: when the blood was drawn, the dose and interval, estradiol, hematocrit, or something unrelated to testosterone altogether. Before changing the dose or giving up on therapy, it’s worth working through these in order.
Is it too early?
Benefits from TRT don’t all arrive at once. Libido and mood usually begin to improve within the first few weeks. Energy can take one to three months. Changes in strength, muscle mass, and body fat build gradually over three to six months and beyond. If you’re only a few weeks in, “not working yet” may simply mean “not long enough.” That’s worth knowing before reading too much into a single follow-up.
Start with when the blood was drawn
For injectable testosterone esters such as cypionate and enanthate, levels peak roughly one to three days after the injection and fall to a trough just before the next one is due. At our clinic we usually test at trough, immediately before the next scheduled dose, because it shows the lowest level your body sees during the cycle. (Guidelines also accept a mid-interval draw. What matters is that the timing is known and kept consistent from test to test.) A draw taken a day or two after injection catches something closer to the peak. That can look reassuringly high even when the trough is inadequate and symptoms are returning late in the week.
A surprising number of “treatment failure” results are actually mistimed draws. Before anything else changes, make sure the next blood draw is scheduled right before the next injection, not whenever is convenient. Our guide to getting an accurate testosterone blood test covers timing in more detail.
Dose and injection interval
The same weekly dose can feel very different depending on how it’s split. A single weekly injection produces a bigger swing between peak and trough than the same total dose split into two smaller injections a few days apart. If symptoms reliably come back in the last day or two before the next dose (lower energy, flatter mood, less drive), that usually points to the interval rather than the dose. Shortening the interval, for example from once weekly to twice weekly, smooths the curve without raising the total weekly dose.
Estradiol (E2) out of range
Testosterone converts to estradiol. Both too little and too much of it can produce symptoms that look exactly like “TRT isn’t working”: low mood, low libido, joint aches, or new breast tenderness. E2 needs its own blood test and its own interpretation, separate from testosterone. For what counts as too high or too low, and how it’s managed, see our article on the dual role of estrogen in men’s health.
SHBG, free, and bioavailable testosterone
Sometimes total testosterone looks adequate on paper, but symptoms persist because the active fraction isn’t. Sex hormone-binding globulin (SHBG) binds a large share of circulating testosterone and makes it unavailable to tissue. When SHBG is unusually high or low, total testosterone stops telling the full story, and free or bioavailable testosterone becomes the more useful number. We explain how these are measured and when to ask for them in our article on free vs total testosterone.
Elevated prolactin
Prolactin is checked less often than testosterone, but it’s worth asking for when symptoms persist. High prolactin can cause low libido, erectile dysfunction, and fatigue on its own, regardless of what the testosterone level shows. It’s also one of the few findings that changes the workup. A persistently raised prolactin, once medication effects and lab artifacts have been ruled out, warrants investigation for a pituitary cause rather than a TRT dose adjustment. If it hasn’t been checked in the last year, it’s a reasonable addition to the next panel.
Hematocrit and red blood cells
This one isn’t about whether TRT is “working” in the symptom sense. It’s a required safety check at every follow-up. Testosterone stimulates red blood cell production. In some men, hematocrit climbs high enough to cause fatigue, headaches, or a general feeling of being unwell that gets mistaken for the testosterone not doing its job. We cover what the numbers mean and when action is needed in our article on TRT, red blood cells, and polycythemia.
Causes that have nothing to do with testosterone
Several common conditions produce symptoms that overlap almost completely with low testosterone, and none of them improve with a higher dose:
- Thyroid dysfunction (both underactive and overactive)
- Obstructive sleep apnea. Undiagnosed sleep apnea is one of the most commonly overlooked causes of persistent fatigue in men already on TRT (see sleep and testosterone)
- Iron deficiency or anemia
- Depression or anxiety, which can blunt libido and energy independent of hormone levels
- Medications, alcohol, and weight. Some antidepressants, opioids, and heavy drinking all affect libido and energy, and so does carrying excess body fat (obesity and low testosterone)
If a complete blood count, ferritin, and thyroid panel, plus a conversation about sleep and mood, haven’t happened recently, they’re worth doing before assuming the testosterone dose is the problem.
Bottom line
“TRT isn’t working” is a symptom report, not a diagnosis. Before the dose changes, the data should come first. Confirm the blood draw was properly timed, check the injection interval against the symptom pattern, and look at estradiol, SHBG, prolactin, hematocrit, and anything that might be unrelated to testosterone. Most of what reads as treatment failure turns out to be one of these, and each one is simple to check at a follow-up visit. If you’re on TRT and still not feeling the benefit you expected, book a follow-up consultation and bring your symptom timeline with you. If you’re outside Bangkok, we also offer online consultations.
References
- Bhasin S, et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2018;103(5):1715–1744.
- Mulhall JP, et al. Evaluation and management of testosterone deficiency: AUA guideline. J Urol. 2018;200(2):423–432.
- Saad F, et al. Onset of effects of testosterone treatment and time span until maximum effects are achieved. Eur J Endocrinol. 2011;165(5):675–685.
- Melmed S, et al. Diagnosis and treatment of hyperprolactinemia: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011;96(2):273–288.
