Blood Tests Before Starting TRT and During Follow-Up

When a patient shows me a blood result taken at three in the afternoon after lunch and says, "My testosterone is low, I want to start injections right away," I usually have to ask them to test again. It's not that I don't believe them; a result taken at the wrong time can lead a man with normal levels to receive medicine he doesn't need. Blood tests before starting TRT therefore have two jobs: to confirm the diagnosis is real, and to record baseline values for safety comparisons later.

Step 1: Confirm that testosterone is genuinely low

• Total testosterone, drawn between 07:00 and 10:00 while fasting. If it is low, repeat it on another day. All guidelines require at least 2 tests.
• SHBG and albumin, to calculate free testosterone in men with borderline totals, obesity, older age, liver disease or thyroid problems. The 2026 EAU guidance supports wider use of SHBG testing to reduce misdiagnosis (read What is SHBG?).
• The lab should use a standardised method. The Endocrine Society recommends methods certified under the CDC Hormone Standardization (HoST) programme, because different labs can give different values.

Step 2: Find the cause

• LH and FSH: if high, the testicles can't produce enough (primary); if low or normal despite low testosterone, the brain is sending too few signals (secondary)
• Prolactin in secondary cases, to look for a pituitary tumour
• Depending on symptoms: iron studies (ferritin, transferrin saturation), thyroid (TSH), and in some men an MRI of the pituitary if testosterone is very low, prolactin is high, or there are eye symptoms and headaches
• Oestradiol when there is breast enlargement or tenderness (see Hormone imbalance in men)
• Semen analysis if you still plan to have children, because TRT suppresses sperm production (see Semen analysis)

Step 3: Baseline values for safety

Besides blood results, I will ask about snoring and sleep apnoea, urinary symptoms, any history of blood clots, and heart disease, which matter just as much as the lab numbers.

1. Confirm it is truly low

• Morning total testosterone, twice
• SHBG, albumin if borderline

2. Find the cause

• LH, FSH
• Prolactin in selected men
• Estradiol if breasts enlarged
• Semen test if planning children

3. Safety baseline

• CBC, hematocrit
• PSA by age
• Glucose, lipids, liver, kidney
• Blood pressure

Preparing for your test

1. Fast for at least 8 hours; plain water is fine.
2. Come for your blood test between 07:00 and 10:00.
3. Sleep well the night before, and avoid hard exercise and alcohol for 1–2 days beforehand.
4. If you are ill, have a fever or have just had surgery, postpone the test.
5. Tell us about every medicine and supplement, especially biotin, which interferes with some lab methods, and any hormones or "test boosters" you have used.
6. If you have used steroids or hormones before, be honest. I'm not judging you, but I need to know to read the results correctly.

What to test on TRT, and when

The timing of the testosterone test depends on the form of medicine:

• Medium-acting injection (enanthate): test mid-way between injections, aiming for the middle of the normal range
• Long-acting injection (undecanoate): test just before the next injection
• Gel: test after at least 1–2 weeks of use, a few hours after applying

Examples of thresholds doctors use: a haematocrit above 54% means stopping or reducing the medicine and looking for the cause, while a PSA rise of more than 1.4 ng/mL within the first 12 months, a PSA above 4.0 ng/mL, or an abnormal prostate on examination should prompt referral to a urologist. Other side effects and how to manage them are in TRT side effects.

1. Before starting
   Confirm diagnosis, baseline

   Morning 7-10 am, fasting; repeat if low

2. First 3-6 months
   First review

   Symptoms, side effects, hormone level, hematocrit, PSA, blood pressure

3. Every 6-12 months
   Once stable

   Hormone level, hematocrit, blood pressure, and PSA by age

4. If symptoms arise
   Test right away

   No need to wait for an appointment

If hematocrit exceeds 54% or PSA rises quickly, your doctor will adjust treatment or refer you.

When to see a doctor, and how the clinic can help

If you already have old blood results, bring them for me to look at, and I'll tell you whether they can be used or whether you should test again. If you are using hormones but have never had any follow-up tests, get tested soon, especially if you have headaches, a flushed face, palpitations or breathlessness.

At Dr. Kris Clinic we offer blood tests before starting and during TRT in line with international guidelines, explain each result clearly and plan your follow-up appointments. Consultations in English are available. If you're not yet sure whether to start, read What is TRT and who is it for?, or if you'd like a general health check at the same time, see Health check-ups for working-age adults.