Does St. John's wort help with hot flashes during perimenopause?

Hot flashes are the signature symptom of perimenopause, affecting around 75 percent of women during this transition. St. John's wort (Hypericum perforatum) is sometimes suggested as a natural option for hot flashes. There is a small amount of preliminary evidence supporting this use, but the overall evidence base is weak and requires an honest assessment before you decide whether to try it.

How St. John's wort works

St. John's wort contains hypericin, hyperforin, quercetin, and kaempferol. Its primary action involves inhibiting the reuptake of serotonin, dopamine, and norepinephrine, working through a mechanism distinct from conventional SSRIs and SNRIs. It also modulates GABA-A and glutamate receptors. Serotonin and norepinephrine are relevant to hot flash physiology: the thermoregulatory center in the hypothalamus is sensitive to serotonergic and noradrenergic tone, which is why some SNRIs (like venlafaxine) are clinically used to reduce hot flash frequency. St. John's wort's similar but distinct serotonin and norepinephrine activity creates a plausible theoretical basis.

What the research shows

A 1999 open-label study by Grube et al. suggested that St. John's wort reduced vasomotor symptoms including hot flashes in perimenopausal women. However, this study was small, unblinded (no placebo control), and has not been replicated in a rigorous randomized controlled trial. Open-label studies are prone to placebo effect, particularly for subjective symptoms like hot flash perception. The evidence remains weak.

For comparison, the strongest evidence for St. John's wort is in mild-to-moderate depression. A 2008 Cochrane meta-analysis by Linde et al. confirmed superiority to placebo and equivalence to standard antidepressants with fewer side effects, and a 2006 study by Kasper et al. supported similar conclusions. Hot flash reduction has not been confirmed to the same standard.

Some women combine St. John's wort with black cohosh for perimenopausal symptoms, and some combination products have been studied. However, the individual contribution of St. John's wort to any hot flash benefit in those combinations is difficult to separate.

Critical drug interactions you must know

St. John's wort has the most extensive drug interaction profile of any supplement commonly used in perimenopause. These interactions are clinically significant:

- SSRIs, SNRIs, and MAOIs: combining these with St. John's wort creates serious risk of serotonin syndrome, which can be life-threatening. - Warfarin: anticoagulant effect is reduced. - Hormonal contraceptives and hormone replacement therapy (HRT): this is particularly important for perimenopausal women. St. John's wort strongly induces CYP3A4, significantly accelerating the metabolism of hormonal medications. If you are using HRT for hot flashes, St. John's wort could reduce its effectiveness. If you use hormonal contraception, it risks contraceptive failure and breakthrough bleeding. - Antiretroviral medications: blood levels may drop to ineffective levels. - Cyclosporine: transplant rejection risk increases. - Digoxin: blood levels are reduced. - Chemotherapy agents: effectiveness may be reduced.

Additional safety notes: St. John's wort increases photosensitivity. It is not appropriate for severe depression, psychotic disorders, or bipolar disorder without provider oversight. It should not be used during pregnancy or breastfeeding. Studies have used 300 to 900 mg per day standardized to 0.3 percent hypericin. Talk to your healthcare provider before starting.

Tracking hot flashes

If you and your provider decide to try St. John's wort, establish a baseline before starting by tracking the frequency, duration, and intensity of your hot flashes for at least two weeks. PeriPlan includes daily symptom logging that makes this tracking simple and creates a reliable record to review with your provider after 6 to 8 weeks. Hot flash frequency can vary naturally across your cycle, so a longer tracking period gives more reliable data.

Other options to consider

For hot flashes, the most well-supported options remain hormone therapy (most effective), followed by non-hormonal prescription options like venlafaxine, paroxetine (the only FDA-approved non-hormonal option), and gabapentin. Among supplements, black cohosh has more consistent evidence than St. John's wort for vasomotor symptoms. Lifestyle measures including keeping a cool environment, wearing breathable clothing, reducing alcohol and spicy food, and managing stress all contribute meaningfully.

When to see a doctor

See your healthcare provider if hot flashes are severe, occur more than seven times per day, significantly disrupt sleep, or substantially affect your quality of life. Effective treatments are available. Also seek care if you develop signs of serotonin syndrome after starting St. John's wort with any other medication.

This content is for informational purposes only and does not replace medical advice. Always consult your healthcare provider about your specific situation.