It used to be the doctor's job to make diagnoses. If you felt ill, you asked your doctor's advice. You were asked a few searching questions, you were examined, maybe had a test or two, and the probable diagnosis was made. Everything was left to the doctor.

Now that's changing. As more and more of us want to take part in all the decisions made about our health (something I strongly agree with), we have been offered the chance to help make our own diagnoses.

The process started with pregnancy tests, bought over the pharmacy counter. Now Superdrug pharmacies have spread the idea to testing for osteoporosis. It just needs, like the pregnancy test, a small sample of early morning urine. It takes around five days to get the result, which lets you know what your chances are of breaking your hip or wrist, or having spinal or other fractures as you grow older. It doesn't give a definite diagnosis but is enough to let your doctor know whether you need further tests, like a bone density scan, that would confirm early osteoporosis.

So you don't get the result yourself. It is sent to your doctor by the pharmacist, who has to be trained in assessing it.

It's not free; the test costs nearly £20, but if it really does catch osteoporosis before it does permanent damage, it may be worth it because today's anti-osteoporosis treatments do work. They prevent the bone loss that would otherwise lead to fractures. The best way to prevent osteoporosis, though, is to plan against it many years ahead - and that means, if you are female, from your teenage onwards. Ten times more women than men develop osteoporosis in middle age and beyond, and this is usually blamed on hormone differences between them.

That's not the whole story. Major reasons for the difference are that many young women are constantly dieting, don't eat healthily and take too little exercise. Trying to look like those skinny fashion models can be disastrous, particularly if they make women cut out milk and bread, the main sources for the calcium they need to build up bone strength.

They need to have plenty of calcium in their bones in their prime years - from 15 to 40 - if they are to maintain good bone strength from their 50s onwards. And that means eating a wide range of calcium-containing foods, including vegetables, fruit, cereals and low fat dairy products like semi-skimmed milk.

But it's no use just sitting around eating and drinking - you need to exercise your muscles to drive the needed calcium into your bones. And that means enough exercise to make you breathless at least three or four times a week. It doesn't really matter what the exercise is, as long as it exercises your whole body.

Nowadays there is plenty to choose from, and it's much easier to find something that you really like and can stick to. I know of women, for example, who have been bored by other forms of exercise, who have turned to line dancing. I hope that it remains popular and isn't just a passing fad because it is just what the doctor ordered.

I'd add any other dancing, aerobics, swimming, cycling, brisk walking, running and athletics to the list of desirable things to do. But I'd also add a warning ... doing anything to excess can be counter-productive. So if you exercise so much that you are under-weight for your height, be careful. You may be doing too much, and that is as bad as too little.

Young women with anorexia nervosa, who drive their weight down to six stones or less by eating too little and exercising far too much, almost always develop osteoporosis later, if they are lucky enough to live that long. Remember Karen Carpenter?

No one should exercise seven days a week: you should always take two days a week off to let your muscles and joints recover. Professional sportsmen - footballers, athletes, swimmers - never train more than five days a week, so neither should amateurs like ourselves.

Until recently, the best medical way to prevent fractures in women with osteoporosis has been hormone replacement therapy (HRT). Now women who don't want, or can't have, HRT, and men (who obviously don't want it!) can be given a "bisphosphonate" - a group of drugs that helps bone to lay down calcium, rather than leak it away. Taken along with food high in calcium content, and perhaps extra calcium tablets, they should be a real boon.

If they only make a small dent in the 12,000 hip fractures a year, that will be a huge savings in human misery and in NHS costs.

Converted for the new archive on 30 June 2000. Some images and formatting may have been lost in the conversion.