Testing and results
Testosterone Blood Tests: Timing, Results and What Is Checked
Understand when to take a testosterone blood test, why a low result is repeated, and what total testosterone, SHBG, LH, FSH and prolactin can show.
The short answer
Quick answer
A diagnostic testosterone blood test is usually taken in the morning, generally between 7am and 10am, when levels are typically highest. A low total testosterone result should normally be repeated on a different morning before a diagnosis is made. The clinician may also request SHBG or calculated free testosterone, LH, FSH, prolactin and other tests based on your symptoms and health history.
Key points
- Timing matters: an afternoon test can be harder to interpret.
- A low total testosterone result is normally confirmed on a separate morning.
- The result must be interpreted with symptoms, medicines, illness and other hormone markers.
- Reference ranges are useful, but they do not replace clinical interpretation.
01
What is the best time for a testosterone blood test?
For men being assessed for possible testosterone deficiency, guidance recommends testing total testosterone in the morning, usually between 7am and 10am, and in a fasting state where practical. Testosterone follows a daily rhythm and can be lower later in the day, especially in younger men.[1,3]
Follow the instructions provided by the clinic or laboratory. Tell the clinician if you work night shifts, were acutely unwell, slept very poorly, or took the test at an unusual time. These details can change how the result is interpreted and whether it should be repeated.
02
Why is a low testosterone result repeated?
Testosterone varies between days and can fall temporarily during illness, severe calorie restriction or disrupted sleep. A single low reading may therefore not represent your usual level. The European Association of Urology recommends repeating total testosterone on at least two separate occasions when the first result is low and treatment is being considered.[1]
The repeat test should be taken under comparable morning conditions. If the two results differ, the clinician may review timing, laboratory method, recent health changes and whether further testing is needed before reaching a conclusion.
03
What can be checked alongside total testosterone?
Total testosterone is the usual starting measurement. Sex hormone-binding globulin, known as SHBG, affects how much testosterone is bound in the blood. When SHBG is unusually high or low, or when the total testosterone result does not fit the symptoms, calculated free testosterone can add useful context.[1,2]
Luteinising hormone (LH) and follicle-stimulating hormone (FSH) can help distinguish a testicular cause from a problem involving the pituitary or hypothalamus. Prolactin may be checked in selected cases, particularly where sexual symptoms, low testosterone and low or inappropriately normal LH occur. The exact panel should be chosen for the individual rather than applied as a one-size-fits-all package.[1]
- Total testosterone: the main starting measurement
- SHBG and calculated free testosterone: useful when binding levels may affect interpretation
- LH and FSH: help investigate where hormone signalling may be disrupted
- Prolactin: used in selected clinical situations
- Blood count, PSA and other safety tests: considered before or during treatment when appropriate
04
What does a low or borderline result mean?
A number below a laboratory reference range is not a complete diagnosis. The clinician considers the assay, the timing of the sample, repeat measurements, symptoms and factors that can alter SHBG. A borderline total testosterone result may need calculated free testosterone or further investigation rather than an immediate treatment decision.[2,1]
Different laboratories may report different reference ranges and units. Avoid comparing a result with an isolated number from social media or a clinic advertisement. The important question is whether there is a consistent biochemical result that fits the clinical picture and whether a reversible cause has been considered.
05
How should you prepare for the appointment?
Bring a list of prescribed medicines, over-the-counter products and supplements. Note when your symptoms began, whether your libido or erections changed, your sleep pattern, alcohol use, recent weight change and any previous hormone results. Tell the clinician about current or future fertility plans before treatment is discussed.
Mens Health TRT offers an initial telephone consultation before an in-person blood-testing appointment at 4 Brick Lane, London. The consultation is free and is intended to establish whether testing is a sensible next step. It does not guarantee that TRT will be recommended or prescribed.
Questions people ask
Common questions, answered clearly.
Do I need to fast before a testosterone blood test?
Guidelines recommend a morning fasting sample where practical because food intake and timing can affect interpretation. Follow the specific instructions from your clinician or laboratory.
Can I test testosterone in the afternoon?
An afternoon result may be less suitable for diagnosing testosterone deficiency because levels generally vary through the day. A clinician may ask for a repeat sample between 7am and 10am.
Is one low testosterone blood test enough?
Usually not. A low result is normally repeated on a separate morning and assessed alongside compatible symptoms before testosterone deficiency is diagnosed.
What can make testosterone temporarily low?
Acute illness, poor sleep, severe calorie restriction and some medicines can affect testosterone. Weight and long-term health conditions may also influence the result. Tell the clinician about these factors.
Can I buy a testosterone blood test in London?
Mens Health TRT offers in-person blood testing by appointment at 4 Brick Lane, London E1 6RF, after a free telephone consultation. There is no home kit or delivery service.
Sources and editorial standard
Mens Health TRT uses primary clinical guidance and NHS patient information. Sources were checked on 16 July 2026. Clinical guidance can change, so follow advice from the professional responsible for your care.