Many are unaware of the looming change caused by the European Court of Justice decision that insurers can no longer take gender into account when setting premiums.
According to financial comparison site uSwitch.com, one-third of women don't realise their car cover costs are about to rise, while many of those who do massively underestimate the possible increase.
Until now, women have typically paid considerably less for motor insurance because they are generally safer behind the wheel. They are far less likely to drive under the influence of drink or drugs and have fewer accidents. Those they do have tend to be less severe, so they don't make so many expensive claims.
Michael Ossei, uSwitch's personal finance expert, said: "Men will no longer be penalised for their 'boy racer' reputation and will be charged the same as women. For the first time ever, men and women will be driving on a level playing field.
"While millions of male drivers will be celebrating cheaper premiums, female drivers need to brace themselves for significant price rises."
Life insurance for women has traditionally been cheaper too, because they tend live longer and so pay more premiums before they die.
However, one area where their greater longevity has seen women historically do worse is pension annuities (see the panel for how these will be affected).
From Friday, all insurers will be bound to charge both sexes the same for equivalent cover. But since they exist to make a profit, they will not split the difference equally between men's and women's pricing to create new gender-neutral premiums.
Moneysupermarket.com said that, back in September, the average female motor premium was £393, while the typical male paid £508 – a difference of 29%. Men may now start to pay fractionally less, but figures from the Association of British Insurers suggest women could face increases of up to 25% – far more than the 10-15% assumed by many of those taking part in the uSwitch survey.
Matt Morris, senior policy adviser at broker Lifesearch.co.uk, puts the average pre-gender neutral differential between men and women's life premiums at about 15%.
He said: "Prices for men aren't going to go down, and the rises for women are probably going to average out around that."
But that doesn't mean women will no longer be able to get car or life insurance at a reasonable cost.
When it comes to car cover, Ossei said: "It's more important than ever that they shop around to find the best deal at renewal time.
"With over 100 providers on the market, there is a big difference between the cheapest and the most expensive quote. A little bit of research will go a long way towards limiting the financial impact of this judgment."
Morris agrees, saying: "If women can't buy life cover before December 21, they should definitely shop around, as prices are going to move about a lot over the next six months as insurers price and re-price."
The easiest way to do this is using comparison websites, but since they don't all list the same providers, it is worth checking two or three.
Don't just grab the cheapest policy without checking the cover suits your situation, though. Insurance that pays too little when you need it, or doesn't pay out at all, is a waste of money.
One area where women are already benefiting from the move to gender-neutral pricing is pension annuities.
When the time comes to draw your work or personal pension, unless you are in a final salary scheme, whatever remains of your fund after taking the tax-free lump sum must be used to buy an annuity. This one-off purchase will provide a pension for the rest of your life, so it is vital to get the best deal you can.
Traditionally, women have received lower annuity payments because they tend to live longer. However, an industry-wide index compiled by provider MGM Advantage shows that firms have already begun applying the gender equality directive to give women a better deal.
At the end of September, the average annual annuity offered to a woman in good health with a £50,000 pension pot was £2506, while a man in similar health got £2653 – a gap of £147. By November 30, the typical female payout had risen to £2563, against a male payout of £2658 – a difference of £95.
If you are coming up to retirement, don't accept the annuity offered by your pension firm without finding out what other providers offer.
Aston Goodey of MGM Advantage believes annuity rates will continue to move, as gender-neutral pricing takes full effect and providers vie for competitive advantage.
"Seeking financial advice is crucial to ensure you use the most appropriate solutions for your individual requirements as well as securing the best annuity rate," he said.