Natural HRT, safe, effective and made just for you – sounds attractive doesn’t it? It’s often advertised with cheesy photos of happy, youthful-looking couples on sunny beaches. Who wouldn’t choose that type of HRT? Yes, it might cost a lot of money – you get what you pay for after all. Or do you? Let’s explore the term ‘bioidentical’ a little more.


In decades past, the only type of HRT available to women in the UK was that derived from horse’s urine – conjugated oestrogens, or Premarin. Much of the early work around HRT was based on this and it is an effective HRT with minimal side effects.

With time though, animal-derived HRT became less popular and newer types of HRT came to market using oestradiol rather than conjugated oestrogens. Oestradiol is the same hormone that is produced naturally in women and so this type of HRT is said to be body-identical or ‘bioidentical’. Research showed it to be effective and although made in laboratories it is synthesised from plants to mimic a woman’s own hormones. Originally in tablet form, oestradiol is now available in patches and gels and in combinations of HRT at various doses.

So, if you want to use ‘bioidentical’ oestrogen, simply choose an HRT which contains that, rather than conjugated. These are available in the NHS and privately at various doses and as tablets, patches or gels.


Progesterone is a natural hormone produced by women. Most HRTs use a synthetic type (called progestogen) in conjunction with oestrogen to protect the womb lining. This is called combined HRT and is necessary if you have not had a hysterectomy (removal of womb by operation). Synthetic progestogens are low risk, but natural progesterone appears to be even lower. The risk of thrombosis (blood clots) is less likely and there is some evidence that natural progesterone, given by tablet, may be better for breast risk with long term use of HRT. So, if you want ‘bioidentical’ progesterone, choose a combination of HRT that includes it, instead of a synthetic progestogen. This is available in the NHS and privately, although at present not all local areas have it on their recommended formularies for GPs to prescribe.

Compounded or conventional?

So you don’t need to see a private specialist to use “bioidentical”. It’s usually available in the NHS. That’s simple enough.

But here’s where it gets more complicated: some private clinics advertise ‘compounded’ HRT.

That means they mix a collection of hormones just for you. Whilst that sounds attractive and more ‘natural’, it means that you may not know exactly what’s in it and whether the balance is right to protect your womb.

You will also be using an individually-specific mix that is not regulated the way conventional HRT is. The individualised HRT may contain hormones that are not used in conventional HRT because of lack of evidence or safety data (like DHEA) and be given in ways that are not easily measured or assessed, such lozenges or creams.

An example is progesterone, which is very hard to get across the skin, so if you are using a progesterone cream, you may not be getting enough of it to protect your womb.

There is no robust scientific evidence that these compounded hormones are safer than conventional bioidentical HRT and in 2017 the Advertising Standards Authority highlighted that the terms ‘natural’, or ‘safer’ than conventional HRT should not be used.

NICE Guidance in the UK and the British Menopause Society – along with other menopause organisations around the world – specifically caution against its use.

HRT Choices

Ideally, you should be offered a choice of HRT. Many menopause specialists, both private and NHS, are now using conventional bioidentical HRT as their first choice, mainly because side effects and risks are lowest.

Sometimes, though, they do not suit individual women and a change is needed, perhaps to a more synthetic but still low-risk type of HRT.

This is truly ‘individualising care’ and it is what menopause specialists are expert at – tweaking doses, changing types and tailoring HRT until you get one that is not only low-risk, but actually works for you, offering an improvement in symptoms, with few or no side-effects and excellent bleeding control and with regulated, assured treatments.