Testosterone Therapy Monitoring in Bangkok: The Baseline and Follow-Up Bloods That Matter

Men's hormone testing guide · 2026

Testosterone therapy is a long-term commitment with a monitoring schedule attached. Skipping the schedule is where the avoidable harm happens.

By MedEx · Updated September 2026 · Approx. 8-minute read

Quick answer

Before starting testosterone therapy, a proper baseline panel should include two morning total testosterone measurements, LH and FSH, prolactin, a full blood count with haematocrit, PSA where age-appropriate, a lipid profile, HbA1c, liver and kidney function. On treatment, the two markers that most often force a change are haematocrit and symptom response. Monitoring is typically at 3 and 6 months in the first year and annually thereafter, with dose adjustment based on trough or mid-interval levels depending on the preparation. Anyone who may want children should discuss fertility preservation first, because testosterone suppresses sperm production.

In this guide

1. Before you start
2. The fertility conversation comes first
3. The follow-up schedule
4. Haematocrit and the other things to watch

Before you start

The diagnosis has to come first. Two morning total testosterone measurements on separate days, both low, in someone with consistent symptoms — not one afternoon reading. LH and FSH identify whether the cause is testicular or pituitary, which occasionally reveals a treatable condition that removes the need for lifelong therapy.

Baseline safety markers matter because they define what a change means later:

• Full blood count with haematocrit — the single most important monitoring parameter.
• PSA and prostate assessment where age-appropriate, so a later rise can be interpreted.
• Lipids, HbA1c, liver and kidney function — often abnormal at baseline and relevant to overall risk.
• Prolactin, and consideration of pituitary imaging where LH and FSH are low.
• Sleep apnoea screening where symptoms suggest it, since therapy can worsen it.

These can be assembled from a single morning draw through the MedEx lab test catalogue.

The fertility conversation comes first

Exogenous testosterone suppresses LH and FSH, which shuts down the pituitary signals driving sperm production. Sperm counts commonly fall substantially and can take many months to recover after stopping — sometimes longer, and occasionally incompletely.

Anyone who may want biological children should have this discussion before the first dose, not after. Options include deferring therapy, sperm cryopreservation, or alternative approaches that preserve the axis. A baseline semen analysis is worth having on record.

See the male fertility testing guide for what a baseline assessment involves, or discuss options in a confidential doctor consultation.

The follow-up schedule

When to draw the testosterone level depends on the preparation. For injectable esters, a trough or mid-interval sample is used depending on the regimen; for gels, a level a few hours after application. Take the sample consistently — comparing a peak level to a trough level from a previous visit produces a meaningless trend.

Haematocrit and the other things to watch

Erythrocytosis — a rise in red cell mass — is the most common adverse effect and the most frequent reason to reduce the dose, extend the interval, switch preparation or stop. Injectable preparations tend to raise it more than transdermal. It should be checked at every review, and a significant rise investigated rather than ignored.

Prostate. Testosterone does not appear to cause prostate cancer, but it can accelerate an existing one, so baseline and follow-up assessment matters and a significant PSA rise needs urological review.

Sleep apnoea may worsen. Acne, fluid retention and mood change are common early. Testicular volume typically falls, and gynaecomastia can occur through aromatisation — measuring estradiol with a sensitive assay is more sensible than routinely adding an aromatase inhibitor.

Unsupervised therapy sourced without monitoring is where most harm occurs. If you are already on treatment obtained elsewhere, a monitoring panel and a review are worth arranging now — see the functional lab test service or book a specialist teleconsultation.

Frequently asked questions

What tests are needed before starting testosterone therapy?

Two low morning total testosterone measurements on separate days, LH, FSH and prolactin, a full blood count with haematocrit, PSA where age-appropriate, a lipid profile, HbA1c, and liver and kidney function.

How often should testosterone therapy be monitored?

Typically at 3 and 6 months during the first year, then annually, with symptoms, testosterone level, haematocrit, blood pressure and PSA reviewed at each visit.

Why is haematocrit checked on testosterone therapy?

A rise in red cell mass is the most common adverse effect and the most frequent reason to reduce the dose, extend the interval, change preparation or stop treatment.

Does testosterone therapy affect fertility?

Yes. It suppresses the pituitary signals that drive sperm production, and counts can take many months to recover after stopping. Anyone who may want children should discuss this and consider sperm storage before starting.

When should the blood sample be taken relative to my dose?

It depends on the preparation – a trough or mid-interval sample for injectable esters, and a few hours after application for gels. The important thing is consistency, since comparing a peak to a previous trough produces a meaningless trend.

Should I take an aromatase inhibitor with testosterone?

Not routinely. Oestrogen has important roles in bone density and sexual function in men, and suppressing it too far causes problems. Measure estradiol with a sensitive assay and treat symptoms, not numbers.

Sources and further reading

1. Endocrine Society: Testosterone Therapy in Men With Hypogonadism
2. European Association of Urology: Sexual and Reproductive Health guideline
3. MedEx lab test catalogue

Medical disclaimer: This article is general health information and does not replace medical advice, diagnosis or treatment. Laboratory reference ranges differ between laboratories and results must be interpreted alongside your symptoms, medicines and medical history. Speak with a qualified clinician before starting, stopping or changing any treatment. Service details, inclusions and prices can change — confirm them with MedEx before booking.