Drinking Water While Fasting: The Dos and Don’ts 

Intermittent fasting is a popular diet used for weight loss and other potential health benefits. It encourages long periods of fasting with shorter eating windows. Eating is not permitted during the fasting period, but certain liquids, namely water, can be consumed. 

This article will answer common questions about drinking water while fasting for health benefits.

So, should you drink water while fasting? 

The short answer to the question “should you drink water while fasting?” is YES! Whether you're practicing intermittent fasting or simply fasting overnight for a blood test, drinking water is allowed and encouraged.

However, it’s important to note that certain religious fasting practices may not permit drinking fluids while fasting.

Drinking water while intermittent fasting  

You can (and should) drink water while intermittent fasting. Those who practice intermittent fasting alternate between eating and fasting (not eating) on a regular schedule. The most common type of intermittent fasting is a daily eight hour eating window followed by a 16 hour fast. But there are a variety of other fasting patterns.

There is emerging research that intermittent fasting may be more beneficial than other diets for conditions associated with inflammation such as Alzheimer’s and arthritis. Still, additional research is needed. The main benefit of intermittent fasting is weight loss.

Since water does not add calories to the diet, it’s allowed during the fasting period.

Drinking water while fasting for a blood test 

You can drink water while fasting for a blood test. There are no limits on the amount of water you can drink. It’s actually beneficial to drink water leading up to a blood test because it can make it easier to find your vein for the blood draw.

For fasting blood work, it is generally recommended to fast for 10 to 12 hours overnight before getting your blood drawn. Note that not all blood tests require fasting, so check with your healthcare provider for specific recommendations. 

What is a water fast? 

Water fasting is a practice where someone consumes nothing except water for a period of time, usually a few days in a row. The main reason for water fasting is to lose weight. Research has shown that water fasting may improve heart health markers, but these levels were found to rebound after the fasting period ended.

Experts caution that water fasting is difficult to follow and any weight that was lost will likely be regained. It’s also not advised to water fast for more than five days at a time.

It’s not recommended to try water fasting unless first speaking with your healthcare provider. This practice is also not appropriate for those who are pregnant or with eating disorders or disordered eating.

How much water should I drink while fasting? 

While fasting, you should follow the general guidelines for daily fluid intake for adults:

• Men: ~15.5 cups

• Women: ~11.5 cups

Check with your healthcare provider to find out if you should be drinking more or less water.

What is dry fasting? 

Dry fasting involves avoiding all foods and beverages during a fast. Unlike intermittent fasting or fasting for blood work, there is no water allowed during a dry fast.

Supporters of dry fasting claim that it has health benefits such as weight loss, inflammation reduction, and immune support. But experts are quick to point out that there currently isn’t enough research to support these claims.

Is dry fasting risky? 

The main risk of dry fasting is dehydration. Symptoms of dehydration include fatigue, dizziness, and confusion. Dry fasting could also lead to urinary, heart, and kidney problems.

Can I drink anything else while fasting: sparkling water, lemon water, etc.

When intermittent fasting, some people will not eat or drink anything besides water during their fasting window. But zero-calorie drinks such as sparkling water, lemon water, and flavored waters are allowed.

It’s also generally accepted that caffeinated beverages are okay to drink during the fasting window, provided they do not contain any calories. Acceptable caffeinated beverages include plain black coffee or tea with no milk or sugar. However, when fasting for blood work, it’s advised to drink only water. You should follow your healthcare provider's full recommendations about what you are or are not allowed to consume prior to bloodwork or other medical procedures.

What drinks should I avoid while fasting? 

Drinks to avoid for intermittent fasting

When intermittent fasting, beverages that contain calories are avoided during the fasting window. Calorie-containing beverages include regular soda, juices, milk teas, and some sports drinks. Water and zero-calorie drinks like black coffee and unsweetened tea are allowed.

Drinks to avoid for medical fasting 

When preparing for a blood test that requires fasting, it’s recommended to avoid all drinks except for water. So do not drink coffee, tea, juice, flavored waters, or carbonated beverages.

For other types of medical tests that require fasting, ask your healthcare provider for detailed instructions about what you can eat or drink leading up to the procedure.

How Season’s dietitians can help you with your health goals

If you’re curious about fasting because you want to lose weight or support your health, we’re here to help! Working with a Season dietitian gives you a personal guide who can help you find the best eating plan for your unique situation. Find out more here!