Can humans change sex?

A person’s genetic inheritance, their biological sex, is an immutable characteristic. It is possible to change a person’s outward appearance, including bodily features.

No. Humans cannot change sex, which was determined at fertilization (genotype) and during embryonic development (phenotype).

People may change many features about their lives, such as their interests, hobbies, diet, friends or careers. However, some facts are unalterable. A person’s genetic inheritance, their biological sex, is an immutable characteristic. It is possible to change a person’s outward appearance, including bodily features. Clothing, make-up and prostheses might be used by some people to modify how they look. For example, a female might chest-bind in order to minimise breast visibility, although this is associated with negative symptoms such as rib pain or reduced ability to breathe normally (Peitzmeier et al., 2017). Sex hormones (oestrogen and testosterone) can be administered to further alter someone’s appearance and may impact mood or personality because the compounds are psychoactive. Surgery might also be used to alter or remove reproductive organs. 

While the use of exogenous opposite sex hormones and surgery is known as ‘medical transitioning’, these do not change a person’s underlying biological sex. 

Interventions are sex-dependent, and might include (Coleman et al., 2012):

TestosteroneOestrogen (+/- anti-androgen)
Double-mastectomyBreast implants 
Cosmetic surgery to face Cosmetic surgery to face & trachea

There are also a number of plastic surgery procedures that attempt to cosmetically replicate the genitalia of the opposite sex. These may achieve a desired aesthetic result, but medicine cannot fashion sex organs in a true anatomical and histological sense. Thus there are important differences in function and structure, in terms of physiology and potential medical concerns. For example, the female vagina is a self-lubricating organ, which has the capacity to allow a baby to pass through during childbirth. The vagina does not require any douching. Gynaecologists are the experts in the healthcare of this organ. In contrast, the surgical reproduction of a vagina creates a neovagina, which requires regular dilation and cleaning regimens. The doctors best placed to care for any problems with a neovagina are probably the surgeons who specialise in performing those genital operations. 

The kinds of genital surgery females may also undergo are (Crane, 2016; Boskey, 2020): 

Metoidoplasty – female genitalia is refashioned to replicate the appearance of a small penis, by an operation to release clitoral tissue that has been enlarged from testosterone.

Neophalloplasty – female genitalia is reorganised in a complicated, multi-staged surgical process that aims to first fashion a phallus out of tissue sourced from elsewhere on the patient’s body, then transfer this to the genital region to create a neopenis, with or without a neoscrotum containing prostheses. Typically, skin from the arm, leg or abdomen is grafted and patients undergo multiple operations. Additional implants might be offered to enable mechanical control of the rigidity of the neopenis.

The kinds of genital surgery males may also undergo (Vaginoplasty/Vulvoplasty, no date; Meltzer, 2016):

Neovaginoplasty – male genitalia is altered to replicate the appearance of the vulva and vagina. Most commonly the skin of the penis is inverted to make the neovaginal cavity. Other tissues, such as colon or omentum, might also be used in these surgeries, particularly if a male did not undergo normal penile development due to administration of gonadotropin hormone releasing analogues (‘puberty blockers’) when younger.

Vulvoplasty – male genitalia is refashioned to create a neovulva. It differs from the above procedure as it excludes the surgical fashioning of the neovaginal orifice.

It is important for healthcare practitioners to note that while a biological sex change is impossible – legal sex can be changed. Government and healthcare service policies do allow people to change their ‘sex marker’ or ‘gender marker’ on official documentation such as passports or medical records. Clinicians need to be aware that some patients might therefore have documentation that displays a sex marker incongruent with their reproductive biology. This can pose significant challenges for healthcare communication and care delivery including for children (see FAQ Can a patient change their sex/gender marker on their medical records?). Furthermore, the legal situation in the UK means that a small proportion of adult individuals may have undergone a process to obtain what is known as a Gender Recognition Certificate. These persons may then be issued with an altered birth certificate that does not reflect their biological sex. Persons who hold such certificates are said to have changed ’legal sex’ under a UK law called the Gender Recognition Act 2004 (UK Government, 2004). While someone’s medical or legal documentation may have been amended, their biological sex remains unaltered.


Boskey, E. (2020) How Metoidioplasty Gender Affirming Surgery Works,

Coleman, E. et al. (2012) ‘Standards of Care for the Health of Transsexual, Transgender, and Gender-Nonconforming People, Version 7’, International Journal of Transgenderism, 13(4), pp. 165–232. doi: 10.1080/15532739.2011.700873.

Crane, C. (2016) Phalloplasty and metoidioplasty – overview and postoperative considerations, UCSF Transgender Care and Treatment Guidelines. Available at:

Meltzer, T. (2016) Vaginoplasty procedures, complications and aftercare, UCSF Transgender Care and Treatment Guidelines. Available at:

Peitzmeier, S. et al. (2017) ‘Health impact of chest binding among transgender adults: a community-engaged, cross-sectional study’, Culture, Health & Sexuality, 19(1), pp. 64–75. doi: 10.1080/13691058.2016.1191675.

UK Government (2004) ‘Gender Recognition Act’. Available at:

Vaginoplasty/Vulvoplasty (no date) University of Utah Health. Available at: