How to Properly Hydrate & How Much Water to Drink Each Day | Dr. Andrew Huberman

Summary

There are common rules of thumb for assessing hydration status, like pinching skin or checking nail beds, but these are imperfect measures. Research linking cognitive deficits to low fluid intake may conflate dehydration with insufficient drinking. A simple formula for baseline hydration is 8 oz (240 ml) of fluid per waking hour for the first 10 hours. During exercise, consume fluid equal to your weight in pounds divided by 30 oz per 15-20 minutes. This replaces baseline intake. Metric system: 2 ml per kg body weight per 15-20 minutes. Adequate hydration optimizes physical and cognitive performance.

Takeaways

• 😀 For healthy adults at rest, aim to drink 8 oz (240 mL) of fluid per hour for the first 10 waking hours. This equals about 80 oz or 2.4 liters per day.
• 😊 There are no definitive objective measures of dehydration based on skin turgor, nail beds, etc. These are imperfect and vary greatly between people.
• 🤔 Most data linking mild dehydration to performance impairments is based on reduced fluid intake rather than direct measures of tissue dehydration.
• 😮 Fluid needs are much higher in the first 10 hours after waking compared to evening/night. Adjust intake accordingly.
• 🙂 For exercise, drink your body weight (lbs)/30 oz fluid every 15-20 min on average, or 2 mL/kg body weight for metric.
• 😃 Hydrating well before and during exercise, per the above guidelines, optimizes performance and avoids dehydration.
• 👍 Ingesting fluids consistently in smaller amounts is optimal, but larger boluses spaced further apart can also work.
• 🤓 If exercising for about an hour, the fluid intake can generally replace baseline hourly fluid needs of 8 oz/240 mL.
• 😕 Extreme environments and activities like desert marathons require additional fluid above these baseline recommendations.
• 😉 Simple frameworks for rest, exercise and metric system make hydration recommendations easy to follow.

Q & A

How can you determine if you are dehydrated based on the skin on the top of your hand?

If you pinch the skin on top of your hand and it takes more than 3 seconds to lay back down flat, there is a decent probability you are a little dehydrated and need to ingest some fluid.

What is the difference between measuring dehydration based on water intake versus tissue dehydration?

Measuring based on water intake looks at reductions in the amount of water consumed compared to normal. Measuring tissue dehydration looks directly at the dehydration of body tissues.

What is the baseline fluid intake recommendation for adults at rest?

8 ounces (236 ml) of fluid per hour for the first 10 hours after waking up, which equals about 80 ounces (2.36 liters) per day.

What is the Galpin Equation for fluid intake when exercising?

Take your body weight in pounds and divide by 30 to get the ounces of fluid to consume every 15-20 minutes on average.

How do you convert the Galpin Equation to the metric system?

Consume 2 ml of fluid per kg of body weight every 15-20 minutes on average.

Should you hydrate before exercising?

Yes, following the baseline recommendation of 8 oz/236 ml per hour in the first 10 hours of the day will help establish good hydration before a workout.

Does the Galpin Equation fluid replace or add to the baseline fluid needed?

For about 1-2 hours of exercise it generally replaces the baseline fluid intake. For longer workouts it adds on top of baseline needs.

Do the skin pinch and fingernail press tests definitively show dehydration?

No, they are not perfect or definitive measures of dehydration. But they can indicate the likelihood of some level of dehydration.

Why is the first 10 hours important in the baseline recommendation?

Your fluid needs are much higher in the first 10 hours after waking compared to the evening and nighttime hours.

How should you time your fluid intake when exercising?

Ideally sip consistently throughout exercise according to what works for your sport and gastric emptying rate. But total intake should aim to match the Galpin Equation.