Transgender identity is often associated with gender dysphoria and minority stress. Gender-affirming hormone treatment (GAHT) includes masculinising or feminising treatment and is expected to be lifelong in most cases. Sex and sex hormones have a differential effect on metabolism and CVD in cisgender people, and sex hormone replacement in hypogonadism is associated with higher vascular risk, especially in ageing individuals. Using narrative review methods, we present evidence regarding metabolic and cardiovascular outcomes during GAHT and propose recommendations for follow-up and monitoring of metabolic and cardiovascular risk markers during GAHT. Available data show no increased risk for type 2 diabetes in transgender cohorts, but masculinising GAHT increases lean body mass and feminising GAHT is associated with higher fat mass and insulin resistance. The risk of CVD is increased in transgender cohorts, especially during feminising GAHT. Masculinising GAHT is associated with a more adverse lipid profile, higher haematocrit and increased BP, while feminising GAHT is associated with pro-coagulant changes and lower HDL-cholesterol. Assigned male sex at birth, higher age at initiation of GAHT and use of cyproterone acetate are separate risk factors for adverse CVD markers. Metabolic and CVD outcomes may improve during gender-affirming care due to a reduction in minority stress, improved lifestyle and closer surveillance leading to optimised preventive medication (e.g. statins). GAHT should be individualised according to individual risk factors (i.e. drug, dose and form of administration); furthermore, doctors need to discuss lifestyle and preventive medications in order to modify metabolic and CVD risk during GAHT. Follow-up programmes must address the usual cardiovascular risk markers but should consider that biological age and sex may influence individual risk profiling including mental health, lifestyle and novel cardiovascular risk markers during GAHT.Transgender identity is often associated with gender dysphoria and minority stress. Gender-affirming hormone treatment (GAHT) includes masculinising or feminising treatment and is expected to be lifelong in most cases. Sex and sex hormones have a differential effect on metabolism and CVD in cisgender people, and sex hormone replacement in hypogonadism is associated with higher vascular risk, especially in ageing individuals. Using narrative review methods, we present evidence regarding metabolic and cardiovascular outcomes during GAHT and propose recommendations for follow-up and monitoring of metabolic and cardiovascular risk markers during GAHT. Available data show no increased risk for type 2 diabetes in transgender cohorts, but masculinising GAHT increases lean body mass and feminising GAHT is associated with higher fat mass and insulin resistance. The risk of CVD is increased in transgender cohorts, especially during feminising GAHT. Masculinising GAHT is associated with a more adverse lipid profile, higher haematocrit and increased BP, while feminising GAHT is associated with pro-coagulant changes and lower HDL-cholesterol. Assigned male sex at birth, higher age at initiation of GAHT and use of cyproterone acetate are separate risk factors for adverse CVD markers. Metabolic and CVD outcomes may improve during gender-affirming care due to a reduction in minority stress, improved lifestyle and closer surveillance leading to optimised preventive medication (e.g. statins). GAHT should be individualised according to individual risk factors (i.e. drug, dose and form of administration); furthermore, doctors need to discuss lifestyle and preventive medications in order to modify metabolic and CVD risk during GAHT. Follow-up programmes must address the usual cardiovascular risk markers but should consider that biological age and sex may influence individual risk profiling including mental health, lifestyle and novel cardiovascular risk markers during GAHT.