Does Drinking Water Lower Blood Sugar?

Many people with diabetes believe that good hydration keeps their blood sugar levels in range. It can.

“Yes, drinking water can lower blood sugar levels,” says Chris Szoke, NP, CDCES, a nurse practitioner and diabetes specialist based in Tucson, Arizona. Szoke says that good hydration also improves other aspects of the metabolic health of people with diabetes, such as blood pressure and kidney function.

“There is clear science behind the effects of hydration and blood glucose levels,” says Szoke.

If there’s one thing all health authorities can agree on, it’s that most of us should probably be drinking more water. Optimal hydration is associated with all sorts of comprehensive health benefits. In Everyday Health’s Diabetes Daily forums and other similar communities, you can find many individuals who swear that a few glasses of water can, for example, help prevent or correct hyperglycemia.

“When you become dehydrated, there is less water in your bloodstream and the glucose in your blood becomes more concentrated,” says Szoke. “When you drink enough water, you’re maintaining a healthy balance of water versus glucose in your bloodstream.”

Adequate water also helps your organs perform at their best, says Szoke. For instance, your kidneys: “When your blood glucose levels are high, your kidneys are working overtime. Drinking more water helps allow your kidneys to effectively filter and absorb excess glucose.”

In your own day-to-day life, these effects may seem mild, and a single glass of water may not have an immediate or obvious effect on your blood sugar level. As with other diabetes factors, your glucose meter or continuous glucose monitor (CGM) will be the ultimate judge. But whether or not you see a blood sugar improvement, proper hydration is a worthy health goal.

Drinking too little water, on the other hand, can raise your blood sugar.

Szoke says that poor hydration can lead to a drop in blood pressure, which triggers the release of stress hormones known to spike blood sugar levels.

One small study concluded that three days of water restriction leads to significantly higher blood glucose levels in people with type 2 diabetes.

People without diabetes, by the way, don’t seem to experience the same effect.

At the same time, high blood sugars can also cause dehydration. Excessive thirst and urination are often two of the first major symptoms of type 1 diabetes and type 2 diabetes. When there is far too much glucose in the bloodstream, the kidneys attempt to flush it out, creating extra urine and provoking dehydration.

Severe dehydration can be extremely dangerous for people with diabetes. Dehydration plays a fundamental role in diabetic ketoacidosis (DKA), a potentially deadly diabetes complication ultimately caused by lack of the hormone insulin. Dehydrating illnesses — sicknesses that cause side effects such as diarrhea or vomiting — are the single most common precipitating factor for DKA.

People with diabetes are usually advised to seek medical treatment if they experience vomiting, diarrhea, or any other symptoms that make it difficult to drink fluids. The U.S. Centers for Disease Control and Prevention (CDC) recommend that people with diabetes should go to the emergency room if they have severe vomiting or diarrhea that lasts more than six hours, or if they cannot keep liquids down for as long as four hours.

Your long-term health with diabetes may also be affected by how much water you drink.

“Not drinking enough water could easily be one detail within the many contributing factors, particularly lifestyle habits, that increase a person’s risk of prediabetes, type 2, and all the conditions that make up metabolic syndrome,” says Szoke.

Several studies have suggested that chronic dehydration increases the risk of developing type 2 diabetes, although the data isn’t definitive.

If the connection is real, drinking more water may be an easy treatment to help prevent metabolic dysfunction, including the development of type 2 diabetes.

Chronic dehydration is also linked to a number of other health conditions, including kidney stones, urinary tract infections, high blood pressure, constipation, and headaches.

Szoke recommends swapping caloric drinks or diet sodas for sparkling water or a glass of water with lemon.

“[It’s] one of the healthiest things we can do to start our day!”

Drinking more water may improve the health of people with diabetes and reduce blood sugar levels by supporting weight loss efforts.

Weight loss may be the single most effective treatment for type 2 diabetes, and it can also improve insulin resistance in people with type 1 diabetes.

While drinking extra water isn’t likely to cause significant weight loss on its own, hydration can support weight loss by reducing hunger and speeding up your metabolism. Drinking more water especially helps if you’re replacing caloric beverages. Sweetened drinks like juices and soda, in particular, are highly associated with obesity and type 2 diabetes, and cause immediate blood sugar spikes.

Some common diabetes medications are associated with dehydration:

SGLT-2 inhibitors, which are primarily prescribed to patients with type 2 diabetes, prevent the body from reabsorbing sugar in the kidneys. The body flushes this extra sugar out in the urine, which helps lower blood glucose levels but can also lead to dehydration.
Metformin, the first-line treatment for patients with type 2 diabetes, is known to cause gastrointestinal distress in some patients. Symptoms such as vomiting or diarrhea can lead very rapidly to dehydration and, in extreme cases, to DKA.

Experts also believe that people using GLP-1 medications such as semaglutide and tirzepatide should prioritize proper water intake.

“If you’re taking a GLP-1 with any type of diabetes,” says Szoke, “definitely pay attention to your fluid intake. You will not feel as thirsty, you won’t crave fluids as much. This can lead to daily and overall dehydration.”

Of course, there are many other nondiabetes drugs that can also cause dehydration, such as diuretics, which cause you to urinate more. Diuretics are prescribed for kidney conditions, hypertension, and heart failure, all of which are common in people with diabetes. It may be a good idea to check the listed side effects for your prescription medications or to discuss the possibility of dehydration with your medical team.

Many of the diets frequently adopted by people with diabetes can also increase the risk of dehydration. In particular, the keto, low-carb, and carnivore diets are popular for their low-carb focus, but may lead to dehydration and an electrolyte imbalance — commonly known as the “keto flu.”

Low-carb dieters are advised to drink plenty of water and consider supplementing with minerals such as sodium, potassium, and magnesium. If you’re following a restricted diet, especially one that limits water-heavy ingredients (such as fruit), pay close attention to your water intake.

Finally, people with diabetes should be especially suspicious of the “dry fasting” trend, in which dieters don't drink anything between meals.

The Institute of Medicine of the National Academies recommends that women consume approximately 91 ounces (just over 11 cups) of water total per day, and men about 125 ounces (16 cups). That sounds like a lot, but that’s the total water intake, which includes the water in foods and beverages, not just plain water. The report states that most people get enough water just by obeying their thirst cues.

Even those numbers are just a starting point. There are a lot of factors that go into how much water your body needs — age, weight, diet, and exercise habits all play a role.

“Extra water during exercise is also critical,” adds Szoke, “because you’re losing water through sweat and water helps your body stay cool.”

It’s important not to drink too much water, though, because that can lead to a rare but dangerous condition known as hyponatremia, or water intoxication. Don’t guzzle water if you aren’t thirsty.

Drinking water can lower blood sugar levels by improving your fluid balance and helping your organs perform optimally.
Dehydration — a common side effect of certain diabetes medications and low-carbohydrate diets — can be dangerous, especially the extreme dehydration caused by illnesses like the stomach flu.
Proper hydration is great for the health of people with diabetes, in both the short and long-term, especially if you’re replacing caloric beverages with water.

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