While weight training recently I started to feel woozy and sick, and had to sit down until the feeling passed. Is this a common reactionor something more worrying?
Fred Munster, by email

Exercise is dehydrating, which could be the cause, and it also makes insulin more effective, so the nausea could be because your blood sugar levels have fallen too low. Drink before, during and after exercising. It’s best not to exercise until two hours after eating.

The symptoms may not even have been related to the weight training – you could have had a cold or stomach bug, for example. Your body could also be short of iron, causing you to suffer from iron-deficiency anaemia. If the symptoms persist, see a doctor, who will be able to run a blood test to check your iron levels.