Sex hormone therapy should only be used when prescribed by a doctor and with regular follow‑up; do not buy it online and do not adjust the dose on your own

Cost: Regular doctor visits and blood tests are required. Over a year this can cost several hundred dollars and take up several half‑days of your time.

In plain terms: This section does not discuss whether hormone therapy is appropriate, only how to use it safely. A study followed transgender individuals for about four years. Transgender women taking estrogen had a noticeably higher rate of venous thrombosis than age‑matched controls — 4.1 extra cases per 1,000 people in two years and 16.7 extra cases per 1,000 in eight years. Such risks must be monitored through long‑term follow‑up, and that monitoring only happens when a clinician checks you regularly. When people buy hormones online and adjust doses themselves, there is no one to provide that oversight.

Benefit: Researchers examined electronic medical records from Kaiser Permanente, a large health‑care system. They identified 2,842 transgender women and 2,118 transgender men, with average follow‑up periods of 4.0 and 3.6 years respectively. Each participant was matched to roughly ten cisgender controls based on birth year, race, clinic location, and enrollment date — resulting in 48,686 cisgender men and 48,775 cisgender women. Compared with cisgender women, transgender women showed more venous thromboembolism: 4.1 extra cases per 1,000 people after two years (95% CI 1.6–6.7) and 16.7 extra cases after eight years (6.4–27.5). Compared with cisgender men, the numbers were 3.4 (1.1–5.6) and 13.7 (4.1–22.7) respectively. Rates of ischemic stroke and myocardial infarction were similar across groups. The differences were more pronounced among transgender women who started hormone therapy during the study period. Evidence for transgender men was insufficient to draw conclusions. The authors concluded that “these results may indicate a need for ongoing vigilance regarding the vascular side effects of estrogen in transgender hormone therapy.”

Evidence grade: A

Sources:Getahun D et al. (2018). Cross-sex Hormones and Acute Cardiovascular Events in Transgender Persons: A Cohort Study. Ann Intern Med. https://doi.org/10.7326/M17-2785；国家市场监督管理总局 (2022). 药品网络销售监督管理办法（总局令第 58 号，第九条）. https://www.gov.cn/gongbao/content/2022/content_5717002.htm

Notes: The researchers acknowledged a limitation: they could not determine how many participants obtained hormones outside the health‑care system, so the data on actual medication use are incomplete. This limitation actually underscores why regular medical follow‑up is essential. The study only examined vascular events; it does not address whether hormone therapy should be used or what its overall benefits are — those questions require different evidence. The same principle applies to any use of sex hormones, including birth‑control pills, menopausal hormone therapy, and testosterone replacement. Anyone who buys hormones online, adjusts doses based on internet advice, and never monitors blood clots or liver/kidney function is at risk primarily because there is no medical oversight. In China, the proper route is to consult an endocrinology department or relevant specialist at a licensed medical institution for evaluation, prescription, and follow‑up. 〔17〕