How much should you pee during an Ironman?

During exercise your body produces hormones that reduce the need to pee (part of the old ‘fight or flight’ response). You’re also likely to be sweating a lot, which again reduces the need to urinate to conserve body fluid. So if you end up peeing a lot during a half or full Ironman, you’re likely drinking too much and might benefit from backing off the fluid intake a touch.

How does sweating help the body?

In terms of what constitutes peeing ‘a lot’, I usually tell athletes it’s not a bad thing to pee once on the bike in a half-distance event, possibly twice in an Ironman. This tends to show that you’re drinking a reasonable amount but not massively overdoing it. Much more than that and I’d say it’s a sign of either taking in too much fluid, or insufficient sodium within that fluid to retain it in your body.

Sodium is crucial for maintaining fluid balance,and also plays an important role in the absorption of nutrients in the gut, maintaining cognitive function, nerve impulse transmission and in muscle contraction.

Hyponatremia: What it is and how you can avoid it

Dehydration and sodium: why replacing salt is crucial

If you don’t pee at all that’s not always a big problem, but it could also show that you’re becoming more dehydrated than is optimal for a good performance, so consider slightly increasing fluid intake.

How much dehydration can you tolerate during an Ironman?

Whatever you do be careful how and when you pee during a race – while many do pee while riding the bike it’s actually against race rules, and can result in a yellow card or stop-and-go penalty if seen by a race referee.

Andy Blow has a few top 10 Ironman and 70.3 finishes and an Xterra World Age Group title to his name. He founded Precision Hydration to help athletes solve their hydration issues. He has a degree in Sport and Exercise Science and was once the Team Sports Scientist for Benetton and Renault F1 teams.

MORE

Does a woman’s hydration needs differ to a man’s?

Can I check my hydration levels via my urine?

Does an endurance athlete’s hydration needs change as they age?

Electrolyte sports drinks: can you overdose?

Ironman nutrition: what to carry on the bike

Ironman run: How can I stop constantly needing to go to the loo?

Andy Blow Sports scientist

About

Andy Blow is a sports scientist with a degree in sports and exercise science from the University of Bath. An expert in sweat, dehydration and cramping, Andy previously worked as the team sports scientist for the Benetton and Renault Formula 1 teams, and remains an adviser to the Porsche Human Performance Centre. He specialises in electrolyte replenishment and founded the company he now runs, Precision Hydration. An elite-level triathlete in his younger days, Andy has finished in the top-10 of Ironman and Ironman 70.3 races, as well as winning an Xterra world title. Andy has also worked alongside Dr Raj Jutley, as well as other top sports scientists, to co-author a number of studies and books which have been published in BMJ Journals, the Journal of the International Society of Sports Nutrition and the Journal of the Endocrine Society.