Last modified on February 15th, 2023
When fasting can you drink water?
There are a couple of reasons you might fast. One is if you want to lose weight or improve your health. Fasting for these reasons is usually called intermittent fasting. You might also have to fast for a blood test or medical procedure.
In both cases, generally, yes, when fasting you can drink water. However, the answer isn’t completely cut and dry, and below, we talk more about what you should know.
When Fasting Can You Drink Water in General?
When fasting can you drink water usually? The answer is typically yes, and we’ll break that down based on the type of fast.
Can You Drink Water When You’re Intermittent Fasting?
Intermittent fasting or IF is one of the significant health trends right now. While it may be popular at the moment, it’s not a new concept. In fact, intermittent fasting is a concept that has roots in ancestral living.
We’ll talk more about what intermittent fasting is, but first:
- You can drink water during intermittent fasting
- You can also have coffee, herbal tea, and other beverages without calories
- The key when choosing beverages is, again, that they have no calories
Water doesn’t affect your insulin or your blood sugar levels. Therefore, drinking it doesn’t break your fast. It’s crucial that you do have water when you’re fasting. It will help if you stay hydrated.
On the other hand, solid foods break a fast, causing your body to go back into its fed state. Your fed state lasts for several hours as you digest food.
What About Dry Fasting?
The one exception with water and fasting is in something called dry fasting. You can’t drink water if you’re doing this method, but it can be dangerous, and it’s not advised to do dry fasting in most cases.
Dry fasting restricts all foods and liquids, including water, for a certain period of time. You can do a dry fast while you’re intermittent fasting, but it can lead to health complications, including dehydration.
Some people do dry fasting because they think it helps with weight loss and immune function as well as cellular regeneration and reduced inflammation.
While there’s a fair amount of research on fasting where water is allowed, there’s not enough known about the possible benefits of dry fasting to recommend it.
Sometimes dry fasting is practiced for spiritual benefits, which is a different scenario. Dry fasting helps some people feel more gratitude and a deeper faith. They use dry fasting for improved awareness and prayer. This is a personal decision.
Dry fasting has possible side effects, including tiredness, irritability, and headaches. You may have trouble focusing and concentrating, and you’ll likely have decreased urination. If you stay hydrated while fasting, you might be able to avoid some of the side effects so you can go longer without breaking your fast.
What is Intermittent Fasting?
Intermittent fasting is an eating pattern. You cycle between periods of eating and fasting. A lot of people like IF because it doesn’t tell them what they should eat. Instead, you don’t face limitations on types of food or calories but restrict yourself based on when you eat.
There are a lot of ways you can practice intermittent fasting. For some people, they’ll do 16-hour fasting periods every day. Another popular pattern is two 24-hour fasts, twice a week.
Ancient hunter-gatherers didn’t have the convenient access to food we do today. There were long periods when they couldn’t eat anything. Humans evolved to function without food for much longer than we do in our modern lives. Fasting is a more intuitive way of eating based on our human evolution than the modern concept of eating three or four meals a day.
Fasting is also something that many religions practice, including Islam, Christianity, and Judaism.
When you fast, it changes your body cellularly and molecularly. Your body adjusts its hormone levels, making your stored body fat more accessible. Your body also starts repair processes, and your gene expression changes.
Some of the particular benefits of intermittent fasting can include:
- Weight loss—research shows intermittent fasting can help you with weight loss and stubborn belly fat without going overboard on your calorie restriction. 
- Insulin resistance—you may be able to reduce insulin resistance with intermittent fasting, meaning you can lower your blood sugar by anywhere from 3-6% and fasting insulin levels as much as 30%. These benefits on your insulin can help protect against the development of type 2 diabetes.
- Inflammation—Inflammation is at the root of so many chronic illnesses and autoimmune diseases.  Studies are showing intermittent fasting has the potential to reduce inflammation markers.
- Heart health—When you practice intermittent fasting, it might reduce inflammatory markers, as mentioned above. Fasting can also reduce bad LDL cholesterol, blood sugar, insulin resistance, and blood triglycerides, which are heart disease risk factors.
- Brain boost—When you fast intermittently, it increases something called BDNF, a brain hormone. When you boost BDNF, it can help your brain grow new nerve cells. There’s evidence boosting BDNF can also protect against developing Alzheimer’s.
- Anti-aging—In animal studies, fasting extends lifespan. Studies in rats show fasting expanded their lives by anywhere from 36-83%. 
- Cellular regeneration—In a 2014 animal study, prolonged fasting can trigger cellular regeneration in mice. In a phase I human trial, researchers found similar effects in people with cancer undergoing chemotherapy. 
- Immune function—Since fasting can help your body regenerate new cells, there’s also the potential to strengthen the immune system. Researchers theorize that fasting removes damaged cells, so your body can more effectively create new ones, helping your immune system function at an optimal level. Since fasting can lower inflammation, that could also help your immune system.
- Healthy skin—In a 2019 review, increased immune function coming from fasting helped with wound healing. Some people feel fasting also helps rejuvenate the look of their skin and slow down or reverse signs of aging. That’s probably because it tends to slow down the aging process when you restrict your calories. 
- Spirituality—There’s a reason fasting is something practiced in the world’s main religions. Fasting is thought to increase your sense of spirituality. Fasting may help improve your sense of gratitude and awareness and provide opportunities for prayer or meditation.
- Autophagy—While it relates to some of the terms above, autophagy is worth understanding more specifically if you’re thinking about fasting. Autophagy is when old parts of your cells are broken down and then recycled. Research in animals shows autophagy may help protect against cancer, heart disease, and Alzheimer’s. Autophagy is thought to prevent damaged parts of your cells from accumulating. This could help prevent cancer cells from growing.
Along with being able to drink water if you’re fasting, at least if you aren’t dry fasting, some of the other beverages that don’t have calories that you can have include:
- Unsweetened teas, including herbal teas
- Sparkling water
- Lemon water
- Flavored water (without calories)
- Unsweetened tea
Drinks you should avoid while you’re fasting can include:
- Sweetened tea
- Sports drinks
- Coffee if it has any cream, milk, or sugar
- Energy drinks
What Breaks a Fast?
The idea of fasting is that you don’t have any food or drinks with calories for a certain period. Along with food and beverages with calories breaking a fast, some supplements could break your fast.
For example, taking protein supplements or branched-chain amino acids (BCAAs) can break a fast. Also, leucine, a particular type of BCAA, signals that it’s not fasting to the brain.
When it’s time to break your fast, the foods you choose do matter.
You should avoid having anything high in carbs or sugar. If you have a high-carb or high-sugar meal, it can spike your blood sugar and cause you to have crashes in energy levels and an upset stomach.
Ideally, when you break your fast, you should have a small portion of healthy fats and protein. For example, avocadoes or eggs can be a good option. These foods take longer for your body to digest, so they won’t create a spike in your blood sugar.
When Fasting for a Blood Test, Can You Drink Water?
Another reason you may have the question “when fasting can you drink water,” is if you have a blood test or medical procedure coming up. If your health care provider tells you to fast before a blood test, this usually means you shouldn’t eat or drink anything for a period of time before that test. You can usually drink water when you’re fasting for a blood test, though.
When you eat or drink as you would normally, what you’re consuming absorbs into your bloodstream. This can potentially affect the results.
Glucose tests are among the most common blood tests your doctor may tell you to fast for. You might also have to fast before a lipid test.
Your doctor will tell you exactly how long you need to fast for, but it’s usually anywhere between 8 and 12 hours. If your doctor tells you to fast, water should be the only thing you have at all. You shouldn’t chew gum or exercise because both can affect blood test results.
Drinking water can be beneficial, though, because it adds more fluid to your veins, so it makes it easier to draw blood.
If you accidentally eat or drink anything besides water, you need to tell your healthcare provider, who will likely want to reschedule your test.
If you have any questions about fasting before a blood test or medical procedure, you should direct them to your healthcare provider.
Final Thoughts—When Fasting Can You Drink Water?
When fasting, can you drink water? The answer is typically yes, and it’s encouraged. For example, if you’re intermittent fasting for your weight or general health, you can absolutely drink water. You just shouldn’t have any beverages or supplements with calories.
If you’re fasting for bloodwork or a medical procedure, you can usually also have water unless your doctor tells you otherwise.
The one exception to drinking water when fasting is if you’re trying dry fasting. Dry fasting is like intermittent fasting, except you don’t have any beverages. However, this can put you at risk of dehydration and isn’t for everyone.