Sip in advance. In the week before the race, keep some water with you and take small sips frequently throughout the day so that you stay well hydrated.
Check your pee. First thing in the morning on race day, check your pee colour. You ideally want it to be a pale straw colour; any darker, and you need to drink more water before leaving to get to the start line.
Drink more in the hours before the race. “It’s recommended that runners drink 5-10ml per kg of bodyweight in the two-to-four hours before the start,” says Shaw. If you weigh 65kg, that means that you want to be drinking anywhere from 325ml to 650ml – at least half of a big bottle – of water at least two hours before you plan to start running. “Use your pee colour to determine if you need more to the higher end or lower end of this range.”
Top up with electrolytes. You may have several hours between first waking up in the morning and crossing the start line, during which time you’re going to have your breakfast and coffee. Shaw recommends keeping a bottle of Lucozade Sport to hand during this time to help keep your fuel tank topped up as it contains carbohydrates and electrolytes to enhance hydration and help maintain endurance performance.
Sip regularly throughout the race. “Sip little and often throughout the 26.2 miles to help your body absorb the fluid without you needing to stop to go to the toilet or giving you stomach discomfort,” Shaw advises. You definitely do not want to glug down a load of fluids at any one point!
Go between water and gels. At races like the London Marathon, there are plenty of water and hydration points. At this year’s race, Lucozade Sport drinks can be found at miles nine, 15, and 21, along with their dual-fuel energy gels at miles 14 and 19.
Take on water with your gels. If you’ve been training with gels, you’ll already have a few with you on race day. If you’re planning on consuming Lucozade Sport gels, however, the brand recommends picking up some water to have alongside them as that can help with their palatability while also contributing to your hydration needs.
Don’t neglect sports drinks. “We recommend consuming a combination of water and sports drinks throughout as you will also lose electrolytes in sweat, in particular sodium,” says Shaw. “If we do not replace the lost sodium, you may be at risk of developing hyponatremia, where the body’s blood sodium levels drop too low. Consuming water alone will not replace the sodium we have lost.” If you’re planning on bringing your own fluids, check out our simple guide to making your own electrolytes.
Focus on rehydrating at the end. Once you finish running, it can be difficult to think about consuming anything – but you need to start rehydrating as soon as possible to get the body back to functioning properly. Shaw says that you need to consume around 1.5 times the amount of fluid that you’ve lost through sweat little and often over the following 24-48 hours.

Running hack: how to hydrate properly during a marathon to feel full of energy