If you have started HRT and wondered which of your supplements still make sense, the honest answer is that most are fine, a couple are worth a rethink, and one is worth avoiding outright. HRT replaces oestrogen, usually with progesterone, to ease menopause symptoms, and the supplement questions around it fall into three tidy groups: the one that interferes, the ones that are simply pointless alongside it, and the ones that genuinely help.
The one to avoid: St John's Wort
St John's Wort, taken for low mood, speeds up a liver enzyme that clears oestrogen and tibolone from your body faster. The practical result is that your HRT can do less than the prescribed dose suggests, and menopause symptoms can creep back while you assume the dose is wrong. This is the clearest supplement to leave off while you are on HRT. If low mood is the reason you were considering it, that is worth raising with whoever prescribes your HRT instead, because there are cleaner options.
The ones that are mostly pointless alongside HRT: phytoestrogens
Soy isoflavones and red clover are plant compounds with mild oestrogen-like activity, and they are marketed hard for menopause. They do not appear to interact with HRT in any harmful way. The issue is simply that the case for adding a weak plant oestrogen on top of actual prescribed oestrogen is thin. If HRT is doing its job, phytoestrogens are usually solving a problem you no longer have.
The ones that genuinely help: bone support
The years around menopause are when bone density falls fastest, and HRT itself helps protect it. A well-evidenced supplement stack sits comfortably alongside: vitamin D with vitamin K2, and magnesium, all of which support how your body handles calcium and builds bone. If your diet is low in calcium, that is worth addressing too, ideally from food first. Omega-3 is a reasonable general addition. None of these interact with HRT; they work in the same direction.
The simple version
Drop St John's Wort. Do not bother stacking plant oestrogens on top of real ones. Lean into the bone-supporting basics if your diet does not already cover them. If you are not sure about a specific combination, the free checker will assess your exact supplements against your HRT and show you the reasoning. And the same plant-oestrogen logic and the St John's Wort warning apply if you are on the contraceptive pill or another medicine rather than HRT.