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Congratulations, you are embarking on your journey to running a marathon! Now you have made the first exciting step, it is time to get your basic training nutrition down. Many runners’ initial thoughts are about calorie intake, protein vs. carbs and basic healthy eating. However, adequate hydration is one of the most important steps to take as you start clocking up those miles. Understanding how to hydrate while running is key.


As you lose fluids throughout exercise you will start to feel the fatigue in your body. Some studies have shown that just a 2% reduction in body weight through dehydration can result in a loss of performance. It goes without saying that to complete a gruelling 26 miles, you are going to need your body to be working at its maximum.


For good health, recommendations are to consume about two litres of fluids each day, mainly from drinks but some also comes from the foods we eat. How much you additionally need to drink while exercising depends on many factors including the length and intensity of your run, environmental conditions e.g. how hot and humid it is and how much you sweat, which can vary enormously between individuals.
Packing a drink to take on your run is always an option, especially in hot weather, but it is only really a necessity if you are running over 45-60 minutes. While there is no hydration rule that fits all, we have added some rough guidelines below.

  • Pre-Run: It is important to be fully hydrated before you start your training, so always keep hydration up by ensuring you are consciously drinking fluids throughout the day. Drink 500–600 ML in the two hours before you start. A useful guide to whether you are well hydrated during the day is to look at the colour of your urine – it should be a pale straw colour.
  • During Run: If you are exercising for more than an hour, a guide could be to drink around 150-300 ML of water every 15–20 minutes during your run to limit fluid losses. Maintaining hydration throughout your run is vital for your performance.
  • After Run: Replacing fluid and salts lost through sweat after a run is really important for recovery, especially as your runs get longer. For people who are recreationally active at a high level and during long, intense exercise a guide is to drink approximately 1.25-1.5l of fluids for every kg of bodyweight lost during your run through sweat. These sweat losses can be calculated and there are tools to help you do this available online. You could try drinking a sports drink to aid recovery.

It is vital to note that drinking too much water can also be dangerous, so it is important to get your hydration strategy right throughout your training as well as on the race day.


There are several options for carrying fluids on your long runs, from handheld bottles, belts that hold water bottles and hydration packs. If you are planning the route locally, you could aim to pass a water fountain, shop, or your parked car to get that hydration you need. Once you have found a good routine that works for you, it will help you plan for the hydration stations on the big day.

*This article provides a general overview and may not apply to everyone. Talk to a qualified sports nutritionist or medic for individual advice.