Alternative menopause therapies are used by 13 per cent of women with hot flushes despite no clinical evidence of benefits, say researchers.

The estimated 490,000 Australian women using alternative medicines for menopausal symptoms are wasting their money, say researchers.

And they warn of potential side effects from the products which they say appear to be no more effective than placebo.

Monash University researchers surveyed 2020 women aged 40-65 between October 2013 and March 2014.

Their findings, published in the Medical Journal of Australia, revealed that 13 per cent had used in the last month at least one complementary and alternative medicine (CAM) to treat vasomotor symptoms such as hot flushes and night sweats.

When the finding is applied to the 3.7 million women in that age bracket, it means 490,000 could have used CAMs, said co-researcher Dr Roisin Worsley.

"There is no clinical evidence that the medicines can help their symptoms," Dr Worsley told AAP.

"A lot of women aren't aware they can cause side effects as well, things like nausea and headaches that you would expect with a lot of supplements."

She said the products, many of which are expensive, were pretty much a waste of money.

The most commonly used CAMs for hot flushes and night sweats were phytoestrogens, plants that are thought to have some "estrogen activity", either as food supplements or concentrated tablets.

"Unfortunately in the clinical studies they don't seem to have any benefit over a placebo," she said, adding the same applied to evening primrose oil, black cohosh and ginseng.

While Dr Worsley said she didn't want to overstate potential risks, she said women who have had breast cancer were advised not to use the supplements because of the unknown long term effects.

Women with mild symptoms were better off avoiding spicy foods, staying in a cool environment and dressing in layers, while medical therapies were available for those with worse symptoms, she said.