FTM Risks and Side Effects

Testosterone at cismale levels has been well-studied. This page sizes each risk against the evidence and links you to what to do about it. For dosing and level targets see FTM Dosages and FTM Target Ranges; for monitoring logistics see FTM Blood Testing.

The risk table

Risk	Size / frequency	Evidence strength	Management
Erythrocytosis (high red blood cells)	~11% exceed Hct 0.50 over 20 years; 0.5% exceed 0.54	Strong, main dose-limiting risk	Dose/route adjustment, quit smoking, weight, treat sleep apnea; short-term phlebotomy
Lipid shifts	low HDL ~6-11 mg/dL; high triglycerides ~21-37; high LDL ~13-18	Moderate, real but small; clinical meaning unclear	Standard cardiovascular prevention (USPSTF); lifestyle
Cardiovascular events (MI/stroke)	Unsure, see below	Weak-moderate	Manage conventional risk factors; quit smoking
Acne	Very common; peaks ~6 months; ~94% no/mild long-term	Moderate-strong	Standard acne care as for cis patients; smooth out T peaks
Scalp hair loss	~1/3 mild, ~1/3 moderate-severe at ~10 years	Moderate	Minoxidil; finasteride with trade-offs (see below)
Sleep apnea	Can worsen/unmask; trans-specific rates unknown	Weak-moderate	Screen if risk factors; sleep study; CPAP reassessment
Weight & composition	~+1.7 kg total; +3.9 kg lean, −2.6 kg fat	Moderate	Lifestyle; not a reason to avoid T
Pelvic pain	~23% of trans adolescents in one cohort; more in surveys	Weak-moderate	Rule out causes; topical estrogen, progestins, physio
Mood	Improves on average	Moderate	Smoother formulation if cyclic symptoms; evaluate broadly
Liver	Modern bioidentical T is not hepatotoxic	Strong (as a non-risk)	Baseline LFTs; no special schedule

Erythrocytosis

Testosterone stimulates red-blood-cell production. Too many red blood cells thickens the blood, that’s erythrocytosis, and it’s the main thing your blood tests watch for. In the largest cohort (a group of people followed over time, 1,073 trans men, 20-year follow-up), 11% exceeded hematocrit 0.50 (hematocrit = the share of your blood made up of red cells) at some point, 3.7% exceeded 0.52, and 0.5% exceeded 0.54 and risk keeps accumulating (10% probability by year 1, 38% by year 10).¹ This is why WPATH SOC8 (Statement 12.17)² asks for hematocrit/hemoglobin monitoring for transmasculine-specific lab monitoring.

What raises your risk: smoking (OR ~2.2), long-acting undecanoate injections (OR ~2.9), higher BMI (OR ~3.7), and older age at start.¹ (OR = odds ratio, how much each factor multiplies your risk.) Injectable forms of raised hematocrit more than gel in the ENIGI cohort.³

What to do about it: check T levels (including peak), lower the dose, shorten the injection interval or switch to transdermal (gel or patches), quit smoking, lose weight if relevant, treat any sleep apnea, and rule out other causes; phlebotomy (having blood taken out) or blood donation is a short-term bridge.⁴ UCSF’s plain-language overview of masculinizing therapy walks through the same actions.

The threshold when this becomes an issue isn't known

The Endocrine Society flags Hct >50% as “very high risk,” while the >54% “pause T” threshold is imported from cis-men TRT (testosterone replacement therapy) guidance, Madsen 2021 explicitly notes it’s unknown whether cis-male limits apply to trans men.[¹][⁵] Follow your prescriber’s threshold; no validated trans-specific number exists (see FTM Evidence Gaps).

Skin and hair

Acne is one of the most common early effects (up to ~81% at 6 months in one cohort), peaks around 6 months/first year, then declines, 94% have no or only mild acne long-term.⁶⁷ Treat it like any acne. gentle skincare, over-the-counter topicals first, then prescriptions via your GP or dermatology. Keeping levels in range and avoiding big injection-interval peaks helps.⁴⁸

Scalp hair loss is genetically determined and common long-term: ~33% mild frontotemporal loss (receding at the temples) and ~31% moderate-severe androgenetic alopecia (male-pattern hair loss) at ~10 years.⁶

Finasteride has a real trade-off

Finasteride and dutasteride block DHT (dihydrotestosterone, testosterone’s stronger byproduct), and DHT drives some of the changes you may want. WPATH SOC8, verbatim: “treatment with a 5α-reductase inhibitor may impair clitoral growth and the development of facial and body hair in trans masculine individuals.”² UCSF adds that the 5 mg dose or dutasteride “may result in excessive testosterone blockade, and resultant sexual side effects and regression of some virilization.”⁴ If you’re early in transition and want bottom growth and facial hair, discuss timing carefully. Minoxidil (topical or oral) doesn’t interfere with T and is the lower-stakes option along with microneedling/PRP.⁹

Pelvic pain

Pelvic pain on T is common around ~23% of trans adolescents in one cohort, more in community surveys, and it was community knowledge years before the clinical literature caught up (see FTM Community Knowledge).¹⁰ Causes are mixed and often unclear. atrophic tissue changes (tissue getting thinner and drier), cramping that tracks injection cycles, breakthrough bleeding, pelvic floor issues. Interestingly, it’s associated with slightly lower T levels and breakthrough bleeding so incomplete suppression may contribute.¹¹ Workup (checking for causes) first; treatments used include topical vaginal estrogen, lubricants, progestins or a hormonal IUD, switching to a smoother regimen, and pelvic floor physio.¹² UCSF has a dedicated guideline page on pelvic pain in trans men worth bringing to your clinician.

Myth corrections

• “T damages your liver.” False for modern therapy. The reputation comes from oral 17-alkylated methyltestosterone (an old chemical form of T), a bodybuilding-era drug no longer used. Endocrine Society: “serious hepatic toxicity is not anticipated with parenteral or transdermal testosterone use” (that is, injected or through-the-skin T).⁵⁴ Transient liver-enzyme bumps on blood tests occasionally happen and usually resolve on their own.
• “T causes ‘roid rage.‘” Not at therapeutic (medical) doses. The classic randomized controlled trial (Pope 2000) gave cis men up to 600 mg/week which is 6-12× typical transmasc dosing and even then 84% had minimal psychiatric effects.¹³ In trans men, systematic review evidence shows improved quality of life, less depression and anxiety; aggression doesn’t increase beyond early adjustment, and T level doesn’t track anger.¹⁴¹⁵ Short-term irritability in the first months is common for some (you are having effectively another puberty) and is usually fixed by smoothing peaks such as switching to gel or a shorter injection interval.⁴ See FTM Myths and FAQ.

Drug interactions

• Warfarin/anticoagulants (blood thinners): androgens change anticoagulant activity, more frequent INR (a blood-clotting measure) monitoring when starting or changing dose.
• Insulin/oral hypoglycemics (diabetes pills): androgens can lower blood glucose so insulin needs may drop. Watch for low blood sugar episodes.
• Corticosteroids (steroid anti-inflammatories like prednisone): increased fluid retention, caution with heart, kidney, or liver disease.
• HIV antiretrovirals (HIV medications): NNRTIs (one class of HIV meds) may lower T levels; ritonavir/cobicistat may raise them, mention all meds to your prescriber or check with a trusted medical professional.¹⁶
• Finasteride/dutasteride: no chemical interaction, but it blunts DHT-driven masculinization (see the trade-off above).

Further reading

No single website, this one included, should be your only source of info; these are reputable places to keep reading.

• UCSF Transgender Care - Overview of masculinizing hormone therapy - the friendliest clinical rundown of T’s effects, risks, and monitoring.
• UCSF Transgender Care - Pelvic pain and persistent menses in transgender men - the go-to guide for a too-often-dismissed symptom.
• Madsen et al. 2021 - Erythrocytosis in a large cohort of trans men (open access) - the study behind the red-blood-cell numbers on this page.
• WPATH Standards of Care v8 - the global guideline, including the only transmasculine-specific lab recommendation.
• TransHub - Masculinising hormones - community-written hormone info from Australia.

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Related pages: FTM HRT | FTM Effects | FTM Blood Testing | FTM Long-Term Health | FTM Myths and FAQ | FTM Community Knowledge | Standards of Care

Footnotes

1. Madsen MC et al., Erythrocytosis in a Large Cohort of Trans Men Using Testosterone, J Clin Endocrinol Metab 2021 - https://pmc.ncbi.nlm.nih.gov/articles/PMC8118580/ ↩ ↩² ↩³

2. WPATH Standards of Care v8 (Coleman et al., 2022), Statement 12.17 & Chapter 12 - https://pmc.ncbi.nlm.nih.gov/articles/PMC9553112/ ↩ ↩²

3. Defreyne J et al., Prospective evaluation of hematocrit in GAHT: ENIGI results, Andrology 2018 - https://pubmed.ncbi.nlm.nih.gov/29602229/ ↩

4. UCSF Transgender Care - Overview of masculinizing hormone therapy - https://transcare.ucsf.edu/guidelines/masculinizing-therapy ↩ ↩² ↩³ ↩⁴ ↩⁵

5. Endocrine Society Clinical Practice Guideline (Hembree et al., 2017), Table 10 - https://academic.oup.com/jcem/article/102/11/3869/4157558 ↩ ↩²

6. Wierckx K et al., J Sex Med 2014 (acne & alopecia long-term) - https://pubmed.ncbi.nlm.nih.gov/24344810/ ↩ ↩²

7. Korpaisarn S et al., Effects of testosterone treatment on transgender males, Arch Endocrinol Metab 2021 - https://pmc.ncbi.nlm.nih.gov/articles/PMC8511909/ ↩

8. Rainbow Health Ontario - Guidelines for gender-affirming primary care (4th ed.) - https://www.rainbowhealthontario.ca/wp-content/uploads/2021/09/Guidelines-FINAL-4TH-EDITION-With-2023-Updates.pdf ↩

9. Gender Health SF - GAHT dosing & monitoring guide - https://www.sf.gov/file/ghsf-gender-affirming-hormone-therapy-gaht-dosing-monitoring-guide-primary-care ↩

10. Moussaoui et al., pelvic pain in trans adolescents on T (2022) - https://pmc.ncbi.nlm.nih.gov/articles/PMC9869722/ ↩

11. Grimstad et al. 2023, via ISSM - What is the prevalence of pelvic pain in transgender men? - https://www.issm.info/sexual-health-headlines/what-is-the-prevalence-of-pelvic-pain-in-transgender-men/ ↩

12. UCSF Transgender Care - Pelvic pain and persistent menses in transgender men - https://transcare.ucsf.edu/guidelines/pain-transmen ↩

13. Pope HG, Kouri EM, Hudson JI, Effects of Supraphysiologic Doses of Testosterone on Mood and Aggression, Arch Gen Psychiatry 2000 - https://jamanetwork.com/journals/jamapsychiatry/fullarticle/481565 ↩

14. Baker KE et al., Hormone Therapy, Mental Health, and Quality of Life Among Transgender People: systematic review, J Endocr Soc 2021 - https://pmc.ncbi.nlm.nih.gov/articles/PMC7894249/ ↩

15. Kristensen TT et al., testosterone & aggression in transgender men: systematic review, Horm Behav 2021 - https://pubmed.ncbi.nlm.nih.gov/33309817/ ↩

16. Yelehe M et al., French pharmacovigilance review, Fundam Clin Pharmacol 2022 - https://pmc.ncbi.nlm.nih.gov/articles/PMC9796635/ ↩