The short version
- The National Academies’ adequate intake from drinks is about 13 cups/day for men and 9 for women.
- Exercise and heat raise needs. ACSM advises avoiding losing more than about 2% of body weight in sweat.
- Drink on a schedule during long shifts instead of waiting until you’re thirsty.
I spent years on pool decks, which are hot, humid and deceptively dehydrating, because you don’t notice sweat when you’re around water. Long shifts are similar. You get busy, you skip the break, and by the drive home you have a headache and no energy for anything.
How much do you need?
The National Academies set an adequate intake for total water, from all drinks and food, of about 3.7 liters a day for men and 2.7 liters for women. About 80% of that usually comes from drinks: roughly 13 cups for men and 9 cups for women. Water, milk, coffee and tea all count. Food covers the rest.
These are averages for healthy adults, not exact targets. Body size, activity, heat and medical conditions all change your needs.
Exercise and heat
The American College of Sports Medicine’s position stand on fluid replacement advises avoiding a body-weight loss of more than about 2% from sweating during exercise. Sweat rates vary a lot from person to person, so a practical approach is to drink regularly during long or hot activity and check yourself afterwards. Long, very sweaty sessions may also need sodium (electrolytes), not just water. Drinking huge amounts of plain water during very long events can be dangerous too.
A shift hydration plan
- Drink a glass of water when you wake up.
- Bring a refillable bottle and know its size: 20 oz, 32 oz.
- Set checkpoints every 90 minutes or so during your shift. Our hydration planner builds them from your shift times.
- Drink with every meal and break.
- On hot days or physical shifts, add more and consider a drink with electrolytes.
- Taper fluids an hour or two before bed so you aren’t up all night.
Simple checks
- Urine color: pale yellow is generally a good sign. Dark yellow suggests you need more.
- Thirst and headaches late in a shift are often a sign you fell behind.
- Before and after weight for long workouts in the heat: each pound lost is roughly 16 oz of fluid.
Common mistakes
- Saving all your drinking for after the shift.
- Counting only plain water. Milk, tea, coffee and food all help.
- Overdoing plain water during very long, sweaty events without electrolytes.
- Following a generic number when your clinician has given you a fluid limit.
If you have heart failure, kidney disease or another condition where your clinician limits fluids, follow their number, not this lesson.
Do this today (2 minutes)
Put your shift start and end times into the hydration planner and set phone reminders for the checkpoints it gives you.
Questions people ask
Does coffee count toward hydration?
Yes. Moderate amounts of coffee and tea count toward your daily fluids for most people. Water should still be your main drink.
How do I know if I’m dehydrated?
Common signs include thirst, dark yellow urine, headache, fatigue and dizziness. Severe symptoms like confusion, fainting, or not urinating need urgent medical care.
Do I need electrolyte drinks?
For everyday life, usually not. For long, hot, very sweaty shifts or workouts lasting more than about an hour, electrolytes can help replace sodium lost in sweat.
Sources
- National Academies. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate, 2005.
- American College of Sports Medicine. Exercise and fluid replacement. Med Sci Sports Exerc, 2007.
- U.S. Departments of Agriculture and Health and Human Services. Dietary Guidelines for Americans.
Education only. Not medical advice. Confirm with your clinician.