Monitoring · Testosterone replacement therapy
TRT is not a prescription you collect and forget. It is a treatment that needs monitoring for as long as you are on it, and the reason is simple: one marker, haematocrit, rises in a significant minority of men and is the commonest reason treatment has to be paused or stopped. Alongside it sit the questions that decide whether the dose is right (testosterone at trough, free testosterone and SHBG), whether the side effects are manageable (oestradiol, PSA), and whether the cardiovascular and metabolic picture is improving or drifting. British Society for Sexual Medicine guidance sets the schedule at three, six and twelve months, then annually, and this page follows it.
Venous draw at 103 UK clinics or at home. Report within 48 hours of the lab receiving your sample. No GP referral needed.
Last reviewed 17 September 2026
The short answer
Monitor haematocrit and haemoglobin, total and free testosterone with SHBG, oestradiol, PSA (from 40, or younger with family history), ApoB and full lipids, HbA1c, liver and kidney function, and blood pressure, which is not a blood test and matters as much as any of them. Test at three months after starting or any dose change, again at six and twelve months, then once a year. Draw at trough, in the morning, fasted. A single number out of context means very little; the trend against your own previous results is what tells you whether this is working.
Contact your prescriber promptly if
Your haematocrit is above 54 percent, you have calf pain or swelling, sudden breathlessness or chest pain, a severe headache, or new visual symptoms. Thickened blood raises clot risk and is the specific hazard of testosterone treatment. Also raise it with your prescriber if PSA rises by more than 1.4 ng/mL in a year or crosses their referral threshold, or if you develop new breast tenderness or swelling.
What to monitor
| Marker | Why it is monitored on TRT | What to look for | Panel |
|---|---|---|---|
| Haematocrit and haemoglobin | Testosterone stimulates red cell production. Erythrocytosis is the commonest adverse effect of TRT and the usual reason treatment is paused, reduced or switched from injections to a gel | Above 52% warrants review; above 54% is the accepted threshold for stopping or reducing, and sometimes venesection. Injections raise it more than gels or creams | All panels |
| Total testosterone | Confirms the dose is in range. Most guidance aims for the mid-normal range for a young man, measured at trough | Take it immediately before your next injection, or 3 to 6 hours after a gel, consistently each time. Comparing a trough to a peak is the most common mistake people make with their own results | All panels |
| Free testosterone and SHBG | Total testosterone can look fine while the free fraction is low, or vice versa. SHBG is the reason, and it is altered by obesity, thyroid disease, liver disease and oral medications | A high SHBG with a normal total and low free testosterone explains why symptoms persist at an apparently adequate dose | Ultimate and Signature |
| Oestradiol | Testosterone aromatises to oestradiol, which men need. Too high causes water retention, breast tenderness and mood change; too low, usually from over-using an aromatase inhibitor, wrecks libido, joints, mood and bone density | Both extremes matter. Routine aromatase inhibitor use is not recommended in TRT guidance and causes more problems than it solves | Core hormones in Advanced; full set in Ultimate and Signature |
| PSA (total, free, ratio) | TRT does not cause prostate cancer, but it can stimulate an existing one, so PSA is monitored before starting and during treatment | A baseline before starting, then at 3 to 6 months and annually. A rise above about 1.4 ng/mL in a year, or crossing an age-specific threshold, needs urology review | Ultimate and Signature |
| ApoB, full lipids, Lp(a) | TRT's cardiovascular effect depends on dose and route. Physiological replacement usually improves the metabolic picture; supraphysiological dosing does the opposite | ApoB rather than total cholesterol. A falling HDL with a rising ApoB is the pattern to act on | ApoB and lipids in all; Lp(a) in Ultimate and Signature |
| HbA1c and fasting insulin | Low testosterone and insulin resistance travel together, and correcting testosterone often improves both. This is where the benefit shows objectively | HbA1c falling over 6 to 12 months is a good sign; rising means something else is driving it | HbA1c in all; fasting insulin and HOMA-IR in Ultimate and Signature |
| Liver and kidney (ALT, GGT, eGFR, cystatin C) | Injectable and transdermal testosterone are not hepatotoxic, unlike oral 17-alpha-alkylated compounds, but baseline organ function is still monitored | Cystatin C gives the true kidney reading if you carry significant muscle, where creatinine overestimates impairment | Liver and kidney in all; cystatin C in Ultimate and Signature |
| LH, FSH and fertility | TRT suppresses your own production and sperm count, often to zero. If you may want children, this is the conversation to have before starting, not after | Suppressed LH and FSH on TRT is expected. Fertility usually recovers after stopping but not always, and not quickly | Ultimate and Signature |
Blood pressure is monitored alongside all of this and is not a blood test; testosterone products carry a warning about raised blood pressure, so a home cuff is worth the £25. Guides: testosterone, before starting TRT, PSA, ApoB, cystatin C.
When to test
| When | What it answers | Priority markers |
|---|---|---|
| Before starting | Whether TRT is the right answer, and the baseline everything else is measured against | Two morning testosterone readings, LH and FSH, SHBG, prolactin, haematocrit, PSA, HbA1c, lipids, thyroid, ferritin. Full pre-TRT guide. |
| 3 months | Is the dose right and is haematocrit behaving? | Trough total and free testosterone, SHBG, haematocrit, oestradiol, PSA |
| 6 months | Confirming stability, and whether symptoms match the numbers | The same, plus ApoB and lipids, HbA1c, liver and kidney |
| 12 months | The full annual picture, including the benefits you are supposed to be getting | Everything above plus fasting insulin, hs-CRP, vitamin D, thyroid |
| Annually thereafter | Long-term safety and trend | Full panel. More often if haematocrit has been high or the dose changes |
| After any dose change | Whether the change did what was intended | Wait at least 6 to 8 weeks on injections, 2 to 4 weeks on gels, before retesting |
Every TrueVitals report compares each marker against your previous result, which is what turns a row of numbers into monitoring. Tell us your protocol, the ester or product, the dose and when you last administered it in the lifestyle questions, and the report reads your levels against what you are actually taking rather than against a population range.
Which panel
Advanced
74 biomarkers · £269
Full blood count with haematocrit, total testosterone, oestradiol, ApoB and full lipids, HbA1c, liver, kidney, thyroid, ferritin and hs-CRP. Covers the safety essentials.
View AdvancedThe TRT panel
Ultimate
114 biomarkers · £349
Adds free testosterone and SHBG (without which a total reading is half the story), LH and FSH, PSA with free ratio, cystatin C, Lp(a) and fasting insulin. Every row in the table above.
View UltimateHealth plans
2, 3 or 4 tests · from £706
The 3, 6 and 12-month schedule bought upfront at a lower price per test, each report compared against the last. Built for exactly this.
View health plansClinic draw £19. At-home £39. Morning slot, fasted from 10pm, at trough before your next injection. Train lightly for 48 hours beforehand so liver enzymes are readable.
Honest comparison
A good private TRT clinic monitors testosterone, haematocrit, oestradiol and PSA, which are the essentials, and if yours does that properly you do not need to duplicate it. Two gaps are common. The first is breadth: clinics monitor the treatment, not you, so ApoB, Lp(a), fasting insulin, cystatin C, thyroid, ferritin and vitamin D are rarely included, and those are where the long-term picture lives. The second is NHS TRT, where monitoring is often just a testosterone and a blood count at intervals, with no free testosterone, no SHBG and no oestradiol, which makes it hard to explain why symptoms persist at an apparently fine level. And if you are self-sourcing rather than prescribed, you have no monitoring at all, which is the situation this page is most useful for. Testing on androgens without a prescription.
Read it in context
Result 1
The most important finding on TRT. Options with your prescriber include reducing the dose, splitting injections into smaller more frequent doses, switching to a gel, or donating blood. It is manageable, but only if somebody is looking.
Result 2
Check free testosterone and SHBG first, because a high SHBG can leave the free fraction low at a normal total. If those are fine too, the cause is usually thyroid, ferritin, sleep or mood rather than the dose, and raising the dose will not fix it.
Result 3
HbA1c down, fasting insulin down, ApoB steady, haematocrit in range. This is what working TRT looks like objectively, and it is worth having on paper rather than judging by how you feel in a given week.
FAQs
At three, six and twelve months after starting, then annually, in line with British Society for Sexual Medicine guidance. Retest six to eight weeks after any dose change on injections, or two to four weeks on gels, and more often if haematocrit has been running high.
At trough, immediately before your next injection, in the morning and fasted. On gels, three to six hours after application. The important thing is consistency: comparing a trough with a peak makes results meaningless.
Above 52 percent prompts review and above 54 percent is the accepted threshold for reducing or pausing treatment, because clot risk rises. Injections raise haematocrit more than gels, and smaller more frequent doses usually raise it less than large infrequent ones.
It is worth measuring, because both high and low cause symptoms. What is not recommended is routinely taking an aromatase inhibitor to push it down: guidance advises against it, and crashed oestradiol causes joint pain, low libido, low mood and bone loss.
TRT is not thought to cause prostate cancer, but it can stimulate an existing one, so PSA is checked before starting and monitored during treatment. A rise of more than about 1.4 ng/mL in a year, or crossing an age-specific threshold, warrants urology review.
Yes. It suppresses LH and FSH and usually reduces sperm production, often to zero. If you may want children, discuss this before starting; alternatives such as hCG or clomifene exist, and sperm storage is an option. Fertility often recovers after stopping, but not always and not quickly.
Only if you want the wider picture. Clinics monitor the treatment: testosterone, haematocrit, oestradiol, PSA. A full panel adds free testosterone and SHBG, ApoB and Lp(a), fasting insulin, cystatin C, thyroid, ferritin and vitamin D, which is where the long-term benefit or drift actually shows.
Advanced and Ultimate reports are delivered within 48 hours of the laboratory receiving your sample. Signature takes around 12 working days.
114 biomarkers at trough in one venous draw, at 103 UK clinics or at home, with a report that reads your levels against your protocol and compares them with your last test.
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