If you're on oestrogen for your gender affirming medical treatment, we recommend you take regular blood tests for oestrogen and testosterone levels. This makes sure that the levels of oestrogen in the body are in the desired ranges for feminisation while also minimising any health risks. We can use this information to adjust your oestrogen dosage.
What are the recommended reference ranges?
The following table summarises the recommended reference ranges.
| Pathway | Oestradiol (pmol/l) | Testosterone (nmol/l) |
| Feminising — puberty induction under 14 | 176–345 | <2 |
| Feminising — age 14–16 or slow transition | 176–631 | <2 |
| Feminising — full feminisation | 176–936 | <2 |
What can happen if my hormone levels are outside the desired reference ranges?
If your oestrogen is higher than the reference range then there are greater risks of adverse effects. Hormone levels higher than the desired references don't speed up the desired effects. Your dose will need to be decreased until the hormone levels are within the reference ranges.
If your oestrogen is lower than the reference range, then feminisation effects may not be achieved as quickly or as effectively as desired. Low hormone levels can have health risks. Your dose will need to be increased.
If your testosterone is higher than the reference range, then this could mean that your current antiandrogen is not effective at suppressing testosterone. You may experience unwanted masculinising effects. This may need to adjust or change your antiandrogen medication.
How are the reference ranges chosen?
The desired reference ranges for oestrogen and testosterone are based the optimum levels to achieve feminisation effects, safety, and averages from the population.
The goal of feminising hormone treatment is to have levels of oestrogen and testosterone that match the levels of hormones seen in cis women.
The reference ranges also take into account developmental stage. Adolescents who are undergoing puberty tend to have lower levels of oestrogen than adults. Oestrogen levels tend to be lower in early puberty than in late puberty.
For nonbinary people who are aiming for partial feminisation at a slower rate, the reference ranges for full feminisation may not be appropriate, so lower target ranges for oestrogen are chosen. These ranges are intended to enable partial feminisation effects while also minimising the risks associated with hormone deficiency.
References
Becker, K. L. (2001). Principles and Practice of Endocrinology and Metabolism. Lippincott Williams and Wilkins.
Hembree, W. C., Cohen-Kettenis, P. T., Gooren, L., Hannema, S. E., Meyer, W.J, Hassan Murad, M, Rosenthal, S. M., Safer, J. D., Tangpricha, V., and T’Sjoen, G. G. (2017). “Endocrine treatment of gender-dysphoric/gender-incongruent persons: An Endocrine Society Clinical Practice Guideline”. Journal of Clinical Endocrinology and Metabolism, 102 (11): 3869–3903.
World Professional Association of Transgender Health (2022). “Standards of Care for the Health of Transgender and Gender Diverse People, Version 8”. International Journal of Transgender Health, 23: S1-S259.
To use the finger prick test, you need to be 16 or older and not taking spironolactone. Vitall, the service provider, will send your blood test results directly to your email address.
If you’re taking spironolactone, you’ll need an intravenous blood sample. You can get this through an online blood test service of your choosing, through your GP if they’re willing to help, or at a private clinic/hospital.
If you need a Blood Test Referral Letter to advise your GP or healthcare provider, you can purchase one through the Treatment Recommendation form for £20 or order it separately here. The letter explains why you need blood tests and which ones you’ll need to get.
When you have your results, please submit them in the Treatment Recommendation form for analysis.