Hormones & HRT - Menopause
“Bioidentical” and compounded hormones
Last updated 30 September 2026. How we write this .
Bioidentical describes a hormone's molecular structure, not its safety. Licensed body-identical products exist; custom-compounded versions have less reliable evidence and assurance.
Start here Bioidentical describes a hormone's molecular structure, not its safety. Licensed body-identical products exist; custom-compounded versions have less reliable evidence and assurance.
By the end, you will understand What the different labels mean How identical molecules produce biological effects What licensing establishes Key words used in this lesson MHRA The Medicines and Healthcare products Regulatory Agency, the UK body responsible for assessing medicines and medical devices and for enforcing medicines law. Marketing authorisation The licence a medicine must hold to be legally marketed, granted only after a regulator has assessed evidence of quality, safety and efficacy. A medicinal product that has no marketing authorisation is an unlicensed medicinal product. Full plain-English glossary
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"Bioidentical" means a hormone has the same molecular structure as a hormone made by the human body; it does not mean that a product is automatically safer or more effective. Regulated body-identical hormone products exist, including licensed forms of oestradiol and progesterone. Custom-compounded preparations may lack equivalent evidence, consistency and product-level oversight, so the actual medicine matters more than the marketing label.
What the different labels mean
Oestradiol is an oestrogen, and progesterone is another hormone involved in reproductive signalling. Both can be manufactured with structures identical to those produced in the body. In UK menopause discussions, "body-identical" commonly describes licensed medicines containing these hormones. "Bioidentical" is also used in marketing for bespoke preparations, making the term ambiguous unless the product is identified.
Compounding means making a preparation for a particular person, sometimes by combining ingredients or changing their formulation. It describes how something is prepared, not the molecular identity of its ingredients. A licensed medicine and a compounded preparation can therefore contain the same hormone while having different supporting evidence and quality assurances.
"Plant-derived" describes the starting material. Laboratory processing can convert plant compounds into human-identical hormones, but the body does not simply convert an ordinary plant extract into progesterone. Natural origin, molecular identity and medicine licensing answer three different questions; none should be used as shorthand for the others.
How identical molecules produce biological effects
Hormones act as chemical signals. Oestradiol and progesterone bind to receptors in responsive tissues, influencing gene activity and cellular behaviour. Their effects depend on which receptors are present, the surrounding biology and the amount of hormone reaching that tissue. An identical molecular structure allows familiar signalling; it does not restrict that signalling to desirable effects.
The formulation also matters. A hormone must leave its preparation, enter the body and reach relevant tissues. Processing by the gut and liver can produce a different pattern of exposure from absorption through the skin. Consequently, evidence about one formulation cannot automatically establish the effects of another simply because both contain oestradiol.
The womb lining illustrates why the whole product matters. Oestrogen can stimulate its growth. In someone with a womb, progesterone or another progestogen generally provides essential protection when oestrogen acts throughout the body. Merely including progesterone in a mixture does not establish that enough reaches the lining to provide reliable protection.
What licensing establishes
A UK marketing authorisation requires evidence about a medicine's quality, effectiveness and safety for specified uses. Manufacturing controls address matters such as ingredient identity, strength, stability and contamination. Product information sets out recognised risks, and monitoring continues after authorisation. Licensing provides an accountable evidence framework; it is not a guarantee that nobody will experience harm.
An individually compounded preparation generally does not have its own marketing authorisation. Its particular mixture and formulation may not have undergone the clinical assessment expected of a licensed product. Even when its ingredients are familiar, their combination, absorption and consistency still require scrutiny.
Calling all compounding "unregulated" is too broad: pharmacies and manufacturers can have professional and legal obligations. The important distinction is that oversight of the person or facility does not equal authorisation of the finished medicine. An unlicensed preparation can have a legitimate role when a particular clinical need cannot be met by a suitable licensed option, but bespoke production is not itself evidence of superiority.
What the evidence actually shows
Randomised trials and systematic reviews support menopausal hormone therapy for reducing hot flushes and night sweats. This supports particular hormone interventions for particular outcomes. It does not validate every mixture sold under the bioidentical label, or establish claims about reversing ageing, improving longevity or optimising every aspect of health.
Large trials provide important information about benefits and harms, but they studied particular formulations in particular populations. Their findings need interpretation when considering different hormones, routes or ages. Equally, uncertainty about how precisely older findings transfer is not evidence that a newer preparation is risk-free.
Observational studies suggest that some risks differ between formulations. For example, research supports differences in blood clot risk between oral and transdermal oestrogen. Comparisons involving micronised progesterone also raise potentially important differences from some other progestogens. However, people receiving different products may differ in health and other characteristics, so observational associations cannot settle every comparison.
For custom-compounded combinations, robust comparative trials and long-term safety evidence are limited. Small studies, laboratory measurements and reports of symptom improvement cannot demonstrate that these products are safer than licensed alternatives. NICE guideline NG23 on menopause says women should be told that the efficacy and safety of unregulated compounded bioidentical hormones are unknown. The British Menopause Society states that compounded products do not follow the same MHRA evaluation pathway as licensed medicines, and does not recommend prescribing them because the potential benefits can be achieved with licensed products. The distinction concerns evidence and product assurance, not whether symptoms deserve attention.
Less evidence of harm is not the same as evidence of less harm. A product studied less thoroughly may simply have more unanswered questions.
Why personalisation needs more than a test
Individual care can account for symptoms, medical history, preferences and changing circumstances while using licensed medicines. A preparation does not have to be custom-made for the clinical discussion to be personal. Conversely, a bespoke label cannot show that a particular mixture improves outcomes.
Saliva testing is sometimes marketed as a way to identify an ideal hormonal balance. Hormone measurements vary with timing, biological fluctuations and collection conditions. A saliva result does not directly reveal hormone activity in every tissue, and there is no well-established universal saliva target that proves a compounded menopause preparation is effective or safe.
Blood tests have legitimate uses in specific clinical questions, but their value depends on what is being investigated. A single result cannot capture all the fluctuations described in "Perimenopause and menopause, explained". Repeated testing can create an impression of precision without establishing that decisions based on those measurements produce better health outcomes.
Who these distinctions apply to
These distinctions are especially relevant to people considering or already discussing menopausal hormone therapy. They also help anyone evaluating hormone-related claims: a familiar molecule still needs a reliable formulation and evidence for the proposed purpose. Menopause evidence cannot automatically be transferred to fertility care, gender-affirming care or other endocrine conditions.
Individual relevance depends on factors including whether someone has a womb, their symptoms, age, medical history and previous hormone-sensitive cancer or blood clots. These factors can alter the balance of benefits and harms. Neither "natural" nor "body-identical" overrides them, and evidence supporting symptom relief does not establish a general longevity benefit for people without that clinical need.
Anyone already using prescribed hormones should discuss questions with their care team and should not change medicines based on a consumer device or home hormone result. Seek emergency help for chest pain with breathlessness, sudden facial drooping, or difficulty speaking or moving a limb: call 999. A painful, swollen leg needs urgent advice from a GP or NHS 111; unexpected vaginal bleeding also warrants GP review. Your GP, practice nurse or menopause specialist can explain the NHS and NICE NG23 options for your situation.
How to judge a claim about a product
Start with information that can be checked rather than reassuring adjectives. The original distinction remains useful: route, strength, intended purpose, quality control and individual risk matter more than the marketing label. A convincing explanation connects each claimed benefit to evidence about the actual preparation and the people in whom it was studied.
Identify the ingredients and whether the finished product has a UK marketing authorisation. Check whether supporting research studied this formulation or merely another product containing the same hormone. Distinguish symptom outcomes from hormone measurements, testimonials and laboratory mechanisms. Look for a clear account of recognised harms, remaining uncertainties and the limits of follow-up. Ask whether claimed personalisation addresses a specific clinical need or mainly supports a sales narrative. Testimonials can describe meaningful personal experiences, but they cannot separate a product's effects from symptom fluctuation, expectations or other changes. Claims such as "no risks because it matches your body" are biologically unsound. The useful standard is transparent evidence: what was studied, what improved, what harms were assessed and what remains unknown.
This lesson is general education, not medical advice, and is not a recommendation to start, stop or change any hormone treatment. Your GP, practice nurse or a specialist can discuss what fits your history.
Related in this classroom The studies behind this page Recommendations: unregulated hormone preparations - NICE guideline NG23, updated 2026Sources for this classroom
Educational content only. Not medical advice, diagnosis or treatment. Always consult a qualified healthcare professional before changing your health regimen.