icon
Menu
icon
Home
Services We Treaticon
Testosterone DeficiencyH3 MOTMenopause CareMental Health & Coaching
Health Advice & BlogAbout Us
Contact us
Health advicer

TRT Blood Test Timing: When to Test Testosterone Levels on TRT

When you are using testosterone replacement therapy (TRT), testosterone levels rise after your injection, gel or cream and then gradually fall over time.

When to test on testosterone replacement therapy

Timing depends on the specific preparation you use:

  • Injections: Test on the day of your next dose, immediately before you inject (your “trough” or lowest level)
  • Testogel (topical gel): Test around 4–5 hours after application (approximate “peak” level)
  • AndroForte (scrotal cream): Test around 2–3 hours after application (approximate “peak” level)

Why the timing of your TRT monitoring blood test matters

If you take your blood test at the wrong time, the result may not accurately reflect the testosterone levels in your body during treatment. Correct timing helps your doctor interpret your results safely and accurately (1).

TRT monitoring blood tests should be performed at a consistent point in your treatment cycle. This helps your doctor compare results accurately over time and avoid adjusting your dose based on misleading peak or trough levels.

Consistent timing helps your doctor:

  • Adjust your dose accurately
  • Avoid over- or under-replacement
  • Monitor safety markers such as haematocrit and oestradiol
  • Compare results consistently over time

What is measured in a TRT monitoring blood test?

A TRT monitoring blood test usually measures more than just testosterone. Depending on your treatment and symptoms, your doctor may also monitor:

  • Total testosterone – measures your overall testosterone level
  • Free testosterone – measures the active form available to tissues
  • SHBG (sex hormone-binding globulin) – can affect testosterone availability
  • Oestradiol – important to monitor as TRT can increase oestrogen levels and contribute to side effects in some men
  • Haematocrit and haemoglobin – TRT can increase red blood cell production and thicken the blood, so monitoring is important
  • PSA – routinely measured as part of regular prostate monitoring
  • Liver function and cholesterol – measured as part of general health monitoring

Injectable TRT: testosterone cypionate, enanthate and Sustanon

Testosterone cypionate

Testosterone cypionate is one of the most commonly used injectable TRT medications. Testosterone levels rise after injection and then gradually fall over the following days.

Research shows that a 200 mg injection can raise testosterone to around 38.2 nmol/L (1,100 ng/dL) after four to five days before falling toward lower levels over the following two weeks (1).

Because of this, the best time for a TRT monitoring blood test is immediately before your next injection. This measures your trough level rather than a temporary peak.

Testosterone enanthate

Testosterone enanthate behaves similarly to cypionate. Testosterone levels typically peak within 24–48 hours after injection before gradually declining over the following days or weeks depending on the dosing schedule (3).

For accurate TRT monitoring, blood tests are usually performed immediately before the next injection.

Sustanon (mixed esters)

Sustanon contains a mixture of short- and longer-acting testosterone esters. This can cause testosterone levels to rise sharply after injection before gradually declining over time.

Because of these fluctuations, the most useful monitoring blood test is generally taken immediately before the next injection to assess trough levels.

Topical TRT preparations: Testogel and AndroForte

Testogel (topical testosterone gel)

Testogel is absorbed through the skin and produces a rise in testosterone levels after application. Levels generally peak around 4–6 hours later before gradually falling throughout the day.

For consistent TRT monitoring, blood tests are usually performed around 4–5 hours after applying the gel.

AndroForte (scrotal testosterone cream)

AndroForte is absorbed rapidly through scrotal skin and tends to produce a faster rise in testosterone levels than standard topical gels.

Blood tests are usually checked around 2–3 hours after application to assess treatment levels consistently.

Quick guide: TRT blood test timing

TRT preparation and when to measure

  • Testosterone cypionate - Right before your next injection
  • Testosterone enanthate - Right before your next injection
  • Sustanon - Right before your next injection
  • Testogel - 4–5 hours after application
  • AndroForte - 2–3 hours after application

Frequently asked questions about TRT monitoring blood tests

These are some of the most common questions our team are asked by men already using testosterone replacement therapy.

Do I need to fast before a TRT blood test?

Usually not. Most TRT monitoring blood tests do not require fasting, although fasting may occasionally be requested if cholesterol or glucose testing is being performed at the same time.

Does alcohol affect a TRT monitoring blood test?

Heavy alcohol intake can temporarily affect some blood markers, including liver function tests. It is sensible to avoid excess alcohol for 24 hours before testing.

Can I drink coffee before a TRT blood test?

Yes. Coffee is unlikely to significantly affect your TRT monitoring results.

Can I eat before a TRT blood test?

Yes, unless your doctor has specifically requested a fasting blood sample.

Can I work out before a TRT blood test?

Heavy exercise may temporarily affect markers such as haematocrit, creatine kinase (CK) and prostate specific antigen (PSA). Avoid intense exercise for 48 hours before your blood test where possible.

Does sex affect a TRT blood test?

Sexual activity is unlikely to significantly affect testosterone monitoring results in men already using testosterone replacement therapy. However, ejaculation may temporarily affect prostate specific antigen (PSA) levels, so it is sensible to avoid sexual activity for 48 hours before testing where possible.

Simple tips for your TRT monitoring blood test

  • Time it correctly: Test at the right point for your TRT preparation
  • Be consistent: Test at roughly the same timing relative to your dose each time
  • Hydrate well: Drink water before your appointment so blood draws are easier
  • Go early in the week: Monday or Tuesday testing reduces delays in sample processing

Final thoughts on TRT monitoring blood tests

Regular blood testing is an important part of safe and effective testosterone replacement therapy. Correct timing helps your doctor interpret results accurately, optimise treatment safely, and avoid unnecessary dose adjustments.

Good timing, consistency and ongoing monitoring all help keep your TRT safe, effective and personalised to you. Contact us for more information.

References

  1. Shoskes JJ et al., Transl Androl Urol 2016 – Pharmacology of testosterone replacement therapy preparations
  2. Okano SHP et al., Rev Bras Ginecol Obstet 2025
  3. Pastuszak AW et al., Andrology 2022
  4. Gurayah AA et al., Urology 2022
  5. Turza A et al., Materials 2022
  6. Turza A et al., Molecules 2023

card-image
Testosterone
TRT and High Haematocrit: Managing Thickened Blood
Testosterone can increase red blood cell production, potentially raising haematocrit levels. Learn how raised haematocrit can be monitored and managed safely during TRT.
card-image
Testosterone
Should I consider Testosterone Replacement Therapy?
Testosterone is the primary sex hormone in men. It is responsible for the secondary sexual characteristics we see develop in boys during puberty, and has profound physical and psychological effects on our bodies throughout our lives.
card-image
Testosterone
Top 5 Symptoms of Testosterone Deficiency
With nearly 1 million men already diagnosed with testosterone deficiency in the UK, and testosterone itself being synonymous with the idea of strength, virility, and wellness, it is surprising that so many men who suffer with low levels of testosterone still struggle to obtain a diagnosis.
card-image
Testosterone
Can changes to my diet increase testosterone levels?
Many things impact on our health and wellbeing, including our genetics, conditions or medical problems we develop through life, and of course, the lifestyle choices we make. In terms of testosterone, its loss tends to be multifactorial, including such triggers as age, disease, and also what we eat. There is of course no magic bullet in food or supplement form that will directly result in a boost in testosterone levels, however, there are many foods that will support our bodies and maximise what we can do naturally.