arrow_back Back to Resources

Understanding Blood Tests for TRT

person Marc Campbell calendar_today 20 December 2025 schedule 2 min read verified_user Reviewed by Dr. James Richardson, MBBS, MRCGP - GP with Special Interest in Men's Health

Blood work is the mainstay of management of TRT. It helps you understand what you are testing, what it means, and therefore enables you to have intelligent conversations with your physician regarding your own personal health.

Before TRT: Blood Tests

Before embarking on any form of TRT, you must first begin a full panel of blood work to better determine your starting point and to determine that you are a proper candidate for treatment.

Testosterone Levels

Total Testosterone: This will give you the measure of all the testosterone present in your blood. This value will be measured in nmol/L, ranging from a normal value of 8.64 to 29 nmol/L.

Free Testosterone: The fraction that can be considered to be active in a biological manner. More useful in diagnosing actual hormonal imbalances. Usually between 0.3 to 1.0 nmol/L.

SHBG (Sex Hormone Binding Globulin): A protein that binds along with the hormone testosterone. Higher SHBG means less free testosterone flowing through your veins.

Other Important Markers

  • LH (Luteinising Hormone): Aids in establishing whether the cause is testicular or pituitary
  • FSH (Follicle Stimulating Hormone): A key hormone for fertility assessment
  • Prolactin: Excess levels can inhibit testosterone secretion
  • Oestradiol (E2): While men need some estrogen, too much can be a side effect

Monitoring During TRT

Once you are on TRT, blood tests are done to ensure that the treatment works properly and is also safe for you.

Testing Frequency

  • First 6 months: Every 6-8 weeks to dial in your dose
  • Stable on treatment: Every 3-6 months
  • Yearly: Full panel plus extra markers

Key Markers to Monitor

Haematocrit and Haemoglobin

TRT stimulates the production of red blood cells. Haematocrit above 54% requires dose reduction or phlebotomy. This is one of the most crucial points regarding the safety of the treatment.

PSA (Prostate-Specific Antigen)

Though TRT isn't associated with prostate cancer, one should closely monitor their prostate. It's usual practice to take a baseline reading of the PSA before starting and follow up regularly.

Liver Function Tests

Both ALT and AST values ensure that the liver is clearing medication the way it should. Oral testosterone, though less common, has more effect on the liver compared to injection or gel preparations.

Lipid Profile

TRT may influence cholesterol levels. Such values as total cholesterol, HDL, LDL, and triglycerides should be checked regularly.

Optimal Ranges vs Reference Ranges

There is, however, a crucial difference between "normal" ranges and optimal ranges regarding well-being:

MarkerReference RangeOptimal Range
Total Testosterone8.64-29 nmol/L20-30 nmol/L
Free Testosterone0.17-0.67 nmol/L0.4-0.7 nmol/L
Oestradiol41-159 pmol/L70-110 pmol/L
SHBG18-54 nmol/L20-40 nmol/L

When to Test

To obtain accurate results, the timing of your test matters:

  • Natural testosterone: Test in the morning (7-10am) when levels peak
  • On injections: Test at trough (just before next injection) for consistent results
  • On gels/creams: Test prior to application or at the same time each test

Conclusion

Knowing your blood test results changes you from a passive patient into an active participant with your own health. Do not be afraid to ask your clinic for interpretations of your results, and maintain your own records for monitoring your progress.

Blood TestsMonitoringHealthHormones

Frequently Asked Questions

How often should I get blood tests while on TRT?

During the first six months of treatment, blood tests are typically carried out every 6 to 8 weeks to help your doctor fine-tune your dosage. Once your levels are stable, testing frequency usually reduces to every 3 to 6 months, with a comprehensive annual panel recommended.

What time of day should I have my blood taken?

For the most accurate results, blood should be drawn in the early morning between 7am and 10am, when testosterone levels naturally peak. If you are on injections, your clinic will usually ask you to test at your trough, which is the day of or the day before your next scheduled injection.

What is the difference between total and free testosterone?

Total testosterone measures all the testosterone in your blood, including the portion bound to proteins like SHBG and albumin. Free testosterone measures only the unbound hormone that is biologically active and available for your body to use. Free testosterone is often considered a more accurate indicator of how you actually feel.

Find Your TRT Clinic

Compare UK clinics and find the right provider for your needs.