Estimating How Much Water You Can Drink

If your doctor hasn’t given you a specific water intake recommendation, you can estimate it yourself using the following steps:

Step 1: Track Your Urine Output

• Measure the total amount of urine you pass in a day (24 hours). For example, let’s say you pass 4 cups of urine.

Step 2: Calculate Your Fluid Intake

• Basic Fluid Needs: A general guideline is to drink as much water as you pass in urine plus a little more to account for water loss through sweat, breathing, and bowel movements.

Calculation:

• Urine Output: 4 cups
• Additional Fluid: Generally, adding about 2 cups to your urine output is a safe starting point. This accounts for the water your body loses in other ways.

Total Fluid Intake = Urine Output + 2 Cups = 4 + 2 = 6 cups of water per day.

Step 3: Adjust for Food and Drinks

• Remember that some of your daily water comes from food. For example, if you eat foods like fruits and vegetables, they contribute to your water intake.
• If you estimate that your food provides 2 cups of water (using the food table to estimate), you can reduce your water intake by this amount.

Adjusted Water Intake:

• Total Fluid Intake: 6 cups
• Water from Food: 2 cups

Adjusted Water Intake = 6 cups - 2 cups = 4 cups of water per day from drinks.

Step 4: Monitor Your Weight

• Daily Monitoring: Weigh yourself every day at the same time. If you notice a weight gain of more than 1 pound, you may be retaining water.

Step 5: Adjust for Weight Gain

• If you gain weight, it could indicate fluid retention. For each pound of weight gain, you may reduce your water intake by about 2 cups the next day.

Example:

• Normal Water Intake: 6 cups
• Weight Gain: 1 pound (2 cups of water retention)

Adjusted Water Intake = 6 cups - 2 cups = 4 cups of water the next day.

For Patients on Hemodialysis

If you are on hemodialysis, your ability to remove water is reduced. The steps above can still be used, but you must be more careful to avoid fluid overload. Adjusting your water intake based on your weight and urine output is especially important.

For Patients Not on Hemodialysis

You may have more flexibility in your fluid intake, but it’s still important to monitor your weight and adjust your intake accordingly. The above steps can guide you to stay hydrated without overloading your kidneys.

Practical Tips

• Spread Out Your Drinks: Instead of drinking a lot at once, sip water throughout the day.
• Use Smaller Cups: This can help you drink less without feeling deprived.
• Watch for Hidden Fluids: Remember that soups, ice cubes, and even sauces add to your water intake.

How to Use the Food and Water Content Table

FoodData Central https://fdc.nal.usda.gov/ has the water content listed at the top when you search a food. They have it listed in grams. For reference: One gram of water equals 1 mL. And 240 mL is 1 cup, 120 mL is 1/2 a cup.

Here’s how you can use the table to estimate the water content in the foods you eat:

1. Identify the Foods: Look up the foods you eat daily in the water content table to find their water percentage.
2. Estimate Water Weight: Multiply the weight of the food you consusmed by the water content percentage to calculate the weight of the water in that food.

Example: If you eat 100 grams of cucumber, and the water content is 96%, the water weight would be:

100 grams x 0.96 = 96 grams of water

3. Convert Water Weight to Cups: To convert the weight of the water to cups, use the conversion:

1 gram of water = 0.00423 cups of water.

Example: For 96 grams of water:

96 grams x 0.00423 = 0.41 cups of water

100 grams of cucumber contributes about 0.41 cups of water to your daily intake.

Citations:
1. National Kidney Foundation. Nutrition and Fluid Management for Chronic Kidney Disease Patients. National Kidney Foundation, www.kidney.org/nutrition. Accessed 21 Oct. 2024.
2. Depner, T., et al. “Fluid Management in Hemodialysis: Challenges and Strategies.” American Journal of Kidney Diseases, vol. 45, no. 6, 2005, pp. 1109-1117, www.ajkd.org/article/S0272-6386(05)00706-2/fulltext. Accessed 21 Oct. 2024.
3. Johnson, Richard J., et al. Comprehensive Clinical Nephrology. 6th ed., Elsevier, 2018.
4. U.S. Department of Agriculture, and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. U.S. Government Printing Office, 2020, www.dietaryguidelines.gov. Accessed 21 Oct. 2024.
5. Centers for Disease Control and Prevention. Water and Nutrition: How Much Water Do You Need? CDC, www.cdc.gov/nutrition/data-statistics/water-nutrition.html. Accessed 21 Oct. 2024.
6. Skorecki, Karl, et al. Brenner & Rector’s The Kidney. 11th ed., Elsevier, 2020.
7. Mayo Clinic. Kidney Disease: Water Intake Guidelines. Mayo Clinic, www.mayoclinic.org. Accessed 21 Oct. 2024.