How does drinking water affect your blood sugar levels?

Drinking water won’t lower your blood sugar levels, but it can help you stay healthy by preventing dehydration.

No single food or drink can directly reduce the amount of sugar in your blood. But different foods have different effects on your blood sugar, creating bigger or smaller rises for longer or shorter periods. 

Keeping your blood sugar levels within a healthy range is important. It helps you meet your daily energy needs and reduces your risk of developing chronic metabolic diseases, like type 2 diabetes.

Drinking fewer sugar-sweetened and artificially sweetened beverages is also really helpful. The goal is to opt for water instead.

Below, we’ll explain how drinking water affects your blood sugar levels, both after eating and in the long term. 

We’ll also look at how much water to drink every day, what to do if you need to lower your blood sugar quickly, and some other ways to help manage your blood sugar levels.

How does water affect blood sugar levels?

Drinking enough water plays an important role in managing your blood sugar.

Your blood sugar level is the amount of glucose in your bloodstream relative to the amount of overall liquid that makes up your blood. 

If you’re metabolically healthy, your body is always maintaining a state of “osmotic homeostasis.” It involves keeping your balance of fluids constant throughout your body.

Your body achieves this through hormones, such as vasopressin, and through your thirst response. If you have diabetes, your osmotic homeostasis is challenged, and this leads to high levels of sugar in your blood and urine.  

Making sure you drink enough water can prevent dehydration and help moderate hikes in blood sugar if you have diabetes or prediabetes.

Current research suggests that drinking more water has different effects in the short and long term, and these effects impact different measures of blood sugar.

Research into blood sugar levels after eating

“Postprandial blood sugar” refers to the rises, then the falls, of your blood glucose in the hours after you eat.

Rises and falls are perfectly normal, but having large peaks and dips can lead to fatigue, hunger, and irritability. Over time, they can increase your risk of metabolic diseases, including diabetes.

There’s currently not a lot of research into how drinking water with or after a meal affects our blood sugar levels. The studies that do exist have produced mixed results.

A small randomized trial looked at people who don’t have diabetes, and it measured their blood sugar responses after dehydration.

The researchers concluded that your level of hydration doesn’t affect your blood sugar response after eating.

Research into fasting blood sugar levels

“Fasting blood sugar” is the amount of glucose in your bloodstream when you haven’t been eating. People with hyperglycemia and diabetes have high fasting blood sugar levels.

When we look at large, long-term population studies, there are some strong positive links between drinking enough water and having a reduced risk of hyperglycemia and diabetes.

One study measured hydration levels in almost 4,000 people. It found that the more hydrated people were, the lower their fasting blood sugar and insulin levels.

Another study looked at 3,600 middle-aged people who started out with normal fasting blood sugar levels. The researchers checked again after 9 years. 

Participants who reported drinking less than half a liter of water every day were significantly more likely to have hyperglycemia than those who drank between half and a whole liter.

Those who drank a liter of water or more every day were the least likely to have high blood sugar levels. 

The results showed the same pattern, even after the researchers had accounted for other factors that could affect blood sugar. The team concluded that regularly drinking more water may reduce the risk of developing hyperglycemia.  

Other ways to help manage your blood sugar

You can’t quickly reduce the amount of glucose in your blood by consuming any particular food or drink.

But you can adjust your diet and lifestyle to help reduce your blood sugar after eating and between meals. Here are some options:

• Improve your sleep: Over time, not getting enough sleep can increase your risk of hyperglycemia and type 2 diabetes. Plus, ZOE's research shows that going to bed earlier and sleeping better can improve your blood sugar responses to food the next morning. 

• Exercise more: Getting regular exercise can reduce your fasting blood sugar levels. And unpublished ZOE research has found that exercising after you eat can significantly improve your blood sugar responses. 

• Opt for these foods: Foods rich in healthy protein and fat, like nuts and oily fish, can bring down rises in blood sugar after you eat. And so can high-fiber foods like legumes, vegetables, and whole grains. Over time, these foods can also reduce your fasting blood sugar levels and your diabetes risk.

• Limit these foods: To reduce blood sugar spikes and improve your overall health, try to eat and drink fewer ultra-processed products, like sodas, cookies, most breakfast cereals, and sources of refined grains, like white bread and white rice.

• Slow down when you eat: There’s evidence that fast eaters have higher blood sugar levels than people who eat more slowly. 

If you want to learn more about controlling your blood sugar responses, you can listen to the ZOE Science & Nutrition podcast on the topic.

What to do in an emergency

If you have diabetes, or you know someone who does, it’s crucial to understand what to do if blood sugar gets dangerously high.

If possible, take a blood glucose test. Also, some noticeable signs of high blood sugar, or hyperglycemia, are:

• needing to pee frequently

• feeling thirstier than usual

• feeling tired or weak

• having headaches

• having blurred vision

If you have type 2 diabetes and hyperglycemia, follow these steps:

• Take your insulin: First, make sure you’ve taken your insulin or other medication as prescribed by your doctor. This may be enough to lower your blood sugar to a safe level.

• Move your body: Moderate-intensity exercise, like brisk walking, will reduce your blood sugar level. But avoid very high-intensity exercise, which can temporarily raise your level.

• Stay hydrated: You may need to drink more water than usual as your body tries to get rid of excess sugar in your urine.

• Call an ambulance: If you’re feeling drowsy or confused, or you lose consciousness, someone should call emergency services immediately. 

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How much water should you drink a day?

Dr. Federica Amati, a medical scientist and nutritionist, says there’s no evidence of a perfect amount of water to drink.

“We’re all different, and how much water we each need changes day to day, according to activity level, climate, and other factors,” she explains.

Drinking water whenever we feel thirsty is a good approach to take. However, “As we age, we become less sensitive to our thirst signals, so it’s a good idea to remember to drink,” Dr. Amati adds.

Still, “Forcing ourselves to drink way more than our thirst is not helpful.”

Because hyperglycemia can lead to dehydration, people with prediabetes or diabetes may need to drink more water than average. And increasing, insatiable thirst is one symptom of diabetes.

Summary

Drinking water won’t lower your blood sugar levels, but staying hydrated can help you manage them if you have diabetes.

Other ways to manage your blood sugar include exercising regularly, getting more quality sleep, and having a diet rich in fiber, healthy fats, and protein.

ZOE runs the largest nutrition science study in the world. Our research has shown that how your blood sugar levels respond to different foods is unique to you.

With our at-home test, you can learn how different foods affect your blood sugar and blood fat levels, along with what types of “good” and “bad” bacteria live in your gut.

Take our free quiz to learn more.