Blood Tests Before Starting Trans Hormones

Key points

Baseline tests before starting include blood count, liver, kidneys, electrolytes, lipids, glucose and baseline hormone levels.

It's a good chance to test for HIV, syphilis and hepatitis, and anyone who could become pregnant should have a pregnancy test before starting testosterone.

Timing of follow-up blood tests matters a lot, especially with injections: test at the midpoint between doses so results can be read correctly.

Many patients ask me, "Do I really need blood tests, doctor? My friend has been on hormones for ages and never had anything checked." The answer is that everyone's body is different. Some people have high cholesterol, hepatitis or high blood pressure without knowing it. Starting hormones without this information is like driving without looking at the dashboard. Your first tests are both a safety check and a record of your "baseline" values to compare against in the future.

Why test before starting?

To find contraindications or reasons for caution, such as liver disease, reduced kidney function, high cholesterol or already-thick blood
To choose the right type and form of medicine; for example, someone at risk of blood clots may be better suited to transdermal estradiol than tablets
To have baseline values to compare when monitoring how hormones are affecting you
To look after your overall health, because some people haven't had a check-up in a long time

Commonly recommended tests

Test	What it shows	Who should have it
CBC (complete blood count)	Haemoglobin and haematocrit	Everyone, especially those starting testosterone
Liver function (AST, ALT)	Whether there is liver inflammation	Everyone
Kidney function (creatinine, eGFR)	Whether the kidneys work normally	Everyone
Electrolytes, especially potassium	Risk of high potassium	People who may use spironolactone
Blood lipids	Cholesterol, triglycerides	Everyone
Glucose (FBS or HbA1c)	Diabetes	Everyone
Total testosterone and estradiol	Baseline hormone levels	Everyone
Prolactin	Milk hormone	Recommended by some guidelines for people starting feminising hormones
HIV, syphilis, hepatitis B and C	Infections that may have no symptoms	Recommended for everyone who is sexually active
Pregnancy test	Avoiding testosterone exposure during pregnancy	People with a uterus who could become pregnant

Some people need extra tests depending on their risks, such as LH/FSH in certain cases, a bone density scan if there's a risk of thin bones, or multi-site PCR STI testing (see the 14-pathogen PCR STI test).

DiagramBlood tests before starting hormones, in 5 groups

Baseline before starting

Blood and organs

CBC, hematocrit
Liver: AST, ALT
Kidney: creatinine, eGFR

Metabolic

Blood lipids
Glucose: FBS or HbA1c

Hormones

Total testosterone
Estradiol
Prolactin (some guidelines)

Infections

HIV, syphilis
Hepatitis B and C

Only for some

Potassium, if spironolactone may be used
Pregnancy test, if you have a uterus

Some people may need extra tests by risk, e.g. bone density or multi-site PCR STI tests.

Preparing for your blood test

If glucose and lipids are being tested together, your doctor may advise fasting for 8–10 hours; plain water is fine. (If unsure, ask first, because some tests don't need fasting; see do I need to fast before an HIV test?)
Bring a list of the medicines, hormones or supplements you use, including anything you bought yourself.
If you've been tested before, bring your old results to help with comparison.
Avoid hard exercise and alcohol for 1–2 days before the test, as they can affect liver and muscle values.

If you've used hormones on your own before

You don't need to stop before coming for tests unless your doctor tells you to. Just be open about what you use, the dose and when you last took it. This information helps your results be read correctly and your regimen made safer. I'm not here to scold you; I want to help you from wherever you are right now.

When to have follow-up tests, and when to draw blood for accurate results

In general, follow-up tests are about every 3 months in the first year, then every 6–12 months once things are stable.

The timing of a blood draw has a big effect on how hormone levels are read.

With injections such as testosterone enanthate or injectable estradiol valerate, test at the midpoint between doses. If you test a few days after an injection, the level will look falsely high; if you test just before the next dose, it will look low.
With long-acting injections such as testosterone undecanoate, blood is usually drawn just before the next dose.
With tablets or gel, test at about the same time of day each time, and don't draw blood from the arm where you apply gel.

For target blood levels for each regimen, read feminising hormone therapy (MTF) and masculinising hormone therapy (FTM).

DiagramWhen to draw blood so hormone levels read accurately

Cyclical injections

E.g. Test E, E2 valerate

Draw mid-way between injections
A few days after injecting, levels read falsely high
Just before the next, they read low

Long-acting injection

Testosterone undecanoate

Usually drawn before the next injection
Shows whether the level lasts to the next dose

Oral or gel

Draw at about the same time each time
Not from the arm where gel is applied

Follow up about every 3 months in the first year, then every 6-12 months once stable.

Results to discuss with your doctor before starting

Liver values several times above normal, or untreated viral hepatitis
A high haematocrit even before starting testosterone
Very high lipids or glucose, or uncontrolled high blood pressure
Reduced kidney function or high potassium in someone who may use spironolactone

Most of these results don't mean you can never use hormones, but the condition needs to be managed first or alongside treatment, and the medicine chosen carefully.

Where to get tested

Dr. Kris Clinic offers blood tests before and during hormone therapy, with a doctor explaining your results and planning your medication, for trans women, trans men and non-binary people. If you live elsewhere in Thailand, you can have blood taken near home and bring the results to an online consultation, and English-speaking consultations are available. For the full overview, read gender-affirming hormone therapy (GAHT).

Frequently asked questions

Do I need to fast before the test?

If glucose and lipids are tested together, fasting for 8–10 hours is usually advised, with plain water allowed. Hormone, HIV, liver and kidney tests mostly don't require fasting. Asking the clinic before your appointment is the clearest way to know.

I'm on injections. Which day should I have my blood taken?

Generally at the midpoint between doses. For example, if you inject every 2 weeks, test around day 7 after the injection so the result reflects your true average level.

If my blood test is abnormal, does that mean I can't use hormones?

Not necessarily. Many conditions can be managed alongside hormone therapy, or a safer medicine and form can be chosen. Your doctor will explain what applies to you.

References

Hembree WC, et al. Endocrine Treatment of Gender-Dysphoric/Gender-Incongruent Persons: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2017;102(11):3869–3903.

Coleman E, et al. Standards of Care for the Health of Transgender and Gender Diverse People, Version 8. Int J Transgend Health. 2022;23(Suppl 1):S1–S259.

Deutsch MB, ed. Guidelines for the Primary and Gender-Affirming Care of Transgender and Gender Nonbinary People, 2nd ed. UCSF Transgender Care; 2016.

This article is for education and does not replace diagnosis or treatment by a doctor. If you have symptoms or concerns, please see a doctor.

Blood Tests Before Gender-Affirming Hormones: What to Test and When

Key points

Why test before starting?