Make sure you know where the drink stations are on the race route. Water and energy drinks will be available, but only take a drink if you need one. If it's hot, there will be extra water and showers may be available - use these to cool yourself rather than pouring drinking water over yourself.
The colour of your urine can be a helpful indicator of hydration. Generally, dark urine suggests dehydration, with pale, straw-coloured urine being ideal. If you don't usually drink caffeinated drinks, don't start now as they can be particularly dehydrating if you aren't used to them.
In general, drink when you feel the need and don't gulp large volumes of fluids before, during or after a race - this can result in a condition called hyponatraemia. This happens when the salts in your body are diluted too much and can cause confusion, disorientation and vomiting.
Start the race well hydrated. Drink enough fluids in the week leading up to the race and in particular the day before the event to ensure that you're properly hydrated. Alcoholic drinks can be dehydrating, so don't drink them less than 24 hours before a race.
Choose water or a sports drink. Stick to drinking whatever you have practised with during training.
During strenuous exercise, you can lose between half a litre and two litres of water per hour as sweat. It's important to replace the fluid and salts you lose.
Everyone is different; some people sweat more than others, and some lose more salt in their sweat. Because of this individual variation, it's not possible to give exact advice on how much you should drink during a training session. As a general rule, aim for 120 to 150ml of cold fluid every 10 to 15 minutes. Cooler fluids are recommended because they are usually more palatable and help to lower your core body temperature.
Make sure you know where the drink stations are on the race route. If it's hot, there will be extra water and showers may be available - use these to cool yourself rather than pouring drinking water over yourself.
Most runners don't drink enough during a race and need to rehydrate afterwards, so take on some fluid as soon as you can after crossing the finish line. Although you may feel like celebrating, make sure you're fully hydrated with water or squash before you have any alcohol.