Can Water Help Reduce Blood Sugar? Cleveland Clinic on Diabetes and Dehydration Risks

The FINANCIAL — Drinking more water is often suggested as an easy way to bring blood sugar down, but clinicians say the link between hydration and diabetes is more nuanced. Water is not a substitute for medication and does not directly correct elevated glucose. Still, dehydration can worsen hyperglycemia, increase fluid loss and raise the risk of serious complications.

In a Cleveland Clinic report, diabetes educator Megan Asterino-McGeean, a registered nurse and certified diabetes care and education specialist, said proper hydration can support diabetes care, but it does not treat the disease itself.

The issue affects a large share of Americans. According to the Centers for Disease Control and Prevention’s National Diabetes Statistics Report, an estimated 40.1 million Americans had diabetes in 2023, or 12% of the population.

Another 115.2 million U.S. adults were living with prediabetes, a condition marked by higher-than-normal blood glucose that does not meet the threshold for diabetes.

Diabetes in the United States: CDC Numbers

Americans with diabetes

12% of the population

Adults with prediabetes

2023 estimates

Diagnosed diabetes

People of all ages

Undiagnosed diabetes

27.6% of adults with diabetes

Source: CDC National Diabetes Statistics Report, using 2023 prevalence estimates. Figures refer to diabetes overall, not only Type 2 diabetes.

The CDC estimates that 27.6% of adults with diabetes have not been diagnosed. Some may notice ongoing thirst, frequent urination or fatigue without realizing these symptoms can signal high blood sugar.

Type 2 diabetes makes up the vast majority of cases. It develops when the body becomes resistant to insulin or cannot make enough of it to keep blood glucose in a normal range.

Although hydration is part of daily diabetes management, it cannot fix insulin resistance or insulin deficiency.

How Dehydration Can Push Blood Sugar Higher

Blood glucose is measured as a concentration, usually in milligrams per deciliter (mg/dL).

When the body loses too much fluid, glucose becomes more concentrated in the bloodstream. That can lead to higher blood sugar readings, especially in people whose diabetes is already poorly controlled.

Asterino-McGeean told Cleveland Clinic that dehydration and hyperglycemia can worsen one another.

The problem becomes more serious when blood sugar rises enough that the kidneys start removing large amounts of glucose through urine.

This leads to osmotic diuresis. Glucose pulls extra water into the urine, which increases fluid loss and causes more frequent urination.

If those fluids are not replaced, dehydration can deepen. The drop in circulating fluid volume can further interfere with the body’s ability to regulate glucose and maintain normal circulation.

Drinking water helps restore lost fluid. But taking in large amounts does not endlessly dilute blood sugar, because the kidneys help balance water levels and remove excess fluid.

Lowering persistent hyperglycemia requires treating the underlying cause, which may include too little insulin, medication issues, illness, diet or other factors.

Common Causes of Dehydration, According to the CDC

Dehydration happens when fluid loss exceeds fluid intake. It can affect healthy people too, but diabetes adds extra risk because elevated blood glucose can increase fluid loss through urine.

The CDC’s guidance on water and healthier drinks points to several situations where more fluids are needed.

These include hot weather, more physical activity, fever, diarrhea and vomiting.

For people with diabetes, other important factors include:

• Uncontrolled high blood sugar: Extra glucose in urine increases fluid loss and can cause ongoing thirst.

• Illness and infections: Fever, vomiting, diarrhea and reduced fluid intake can speed up dehydration while stress hormones raise blood glucose.

• Certain diabetes medications: Sodium-glucose cotransporter-2 (SGLT2) inhibitors increase glucose loss in urine and can contribute to fluid depletion.

• Diuretic medications: Drugs used for conditions such as hypertension or heart failure increase urine output.

• Older age: Reduced thirst, medication use and chronic conditions can make hydration harder to maintain.

• Long periods of heat exposure or exercise: Sweating increases fluid needs, especially when drinking is not enough.

The CDC also lists possible effects of not getting enough fluids, including trouble thinking clearly, mood changes, overheating, constipation and kidney stones.

Signs of dehydration can include dry mouth, dizziness, fatigue, less urination and dark urine. Severe dehydration may lead to confusion, a rapid heartbeat or fainting.

Because uncontrolled diabetes can cause frequent urination even as a person becomes dehydrated, urine frequency alone is not a reliable way to judge hydration.

How Much Water Should People With Type 2 Diabetes Drink?

There is no single daily water target that fits everyone with Type 2 diabetes.

Fluid needs vary based on body size, age, activity level, climate, medications and underlying health conditions.

The CDC does not give a universal number of glasses of water specifically for people with diabetes. Its advice focuses on drinking enough fluids and choosing water instead of sugary beverages.

For general reference, the National Academies of Sciences, Engineering, and Medicine set adequate total daily water intake at about 3.7 liters for adult men and 2.7 liters for adult women.

Those amounts include water from both beverages and food, not just drinking water. They are population-level reference values, not personalized prescriptions or minimums for every individual.

People with kidney failure, certain heart conditions or prescribed fluid limits should follow their care team’s instructions instead of general intake targets.

Needs may also change temporarily during illness, very hot weather or prolonged exercise.

Why Water Is Better Than Sugary Drinks for Diabetes Care

The CDC recommends replacing sugar-sweetened beverages with plain water as one practical way to help manage blood glucose and reduce extra calorie intake.

Unlike regular soda, sweetened tea, fruit drinks and many energy drinks, plain water contains no sugar or calories.

Choosing water instead of a sugary drink can lower carbohydrate intake and help avoid the glucose spike that the sweetened beverage might have caused.

That benefit should not be mistaken for water directly lowering an already high blood sugar reading.

Unsweetened tea, plain coffee and sugar-free drinks can also add to fluid intake. Foods with high water content, such as cucumbers, tomatoes, celery and lettuce, can help with hydration as well.

Even so, people with diabetes should check nutrition labels rather than assume a drink promoted as healthy, natural or sports-related is low in sugar.

During certain illnesses or low-blood-sugar episodes, drinks that contain carbohydrates may be appropriate. The right choice depends on the person’s glucose level and treatment needs.

Diabetes Medications Can Influence Hydration

Some commonly prescribed Type 2 diabetes medications increase glucose removal through the kidneys.

SGLT2 inhibitors, including medicines such as empagliflozin and dapagliflozin, reduce blood sugar by limiting how much glucose is reabsorbed into the bloodstream.

More glucose then leaves the body in urine.

This can increase urination and contribute to volume depletion, particularly in older adults, people taking diuretics and those with vomiting or diarrhea.

These medicines also offer proven benefits for some patients with cardiovascular disease, heart failure or chronic kidney disease. They should not be stopped without medical advice.

Another concern is diabetic ketoacidosis, which can sometimes occur in people taking SGLT2 inhibitors even when blood sugar is not extremely high.

Patients on these medications should ask about personalized sick-day rules, including when a temporary pause may be needed.

When Dehydration Becomes a Medical Emergency

Two dangerous complications tied to diabetes and dehydration are diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS).

DKA develops when too little insulin causes the body to burn fat for energy, producing excess ketones and dangerous acidity in the blood.

Although it is more common in Type 1 diabetes, DKA can also occur in Type 2 diabetes.

HHS typically involves extremely high blood glucose, severe dehydration and increased blood concentration. It occurs mainly in people with Type 2 diabetes, especially older adults, and can cause serious neurological symptoms.

Both conditions require urgent medical treatment. Drinking water at home is not a substitute for emergency care.

According to CDC guidance on diabetic ketoacidosis, warning signs include severe thirst, frequent urination, vomiting, abdominal pain, fruity-smelling breath and rapid or deep breathing.

The CDC advises people with diabetes who are sick or whose blood sugar is 250 mg/dL or higher to check glucose every four to six hours and test for ketones.

Emergency care is needed when blood sugar stays at 300 mg/dL or above, when significant ketones are present, or when symptoms such as breathing trouble or ongoing vomiting appear.

DKA can also happen at lower glucose levels, especially in people taking SGLT2 inhibitors. A reading below 300 mg/dL does not rule out an emergency.

CDC Advice for Staying Hydrated During Illness

Illness can be especially difficult for people with diabetes because infections and other physical stressors can raise blood sugar even when eating less.

The CDC’s sick-day advice for diabetes calls for more frequent glucose checks, good hydration and use of an established medication plan.

The agency recommends checking blood sugar about every four hours during illness and writing down the results.

People should also monitor their temperature, keep up nutrition when possible and look for signs of dehydration or unusual ketone levels.

Medication plans deserve special attention. While the CDC’s general guidance says to continue diabetes treatment during illness, some medicines may need to be adjusted or paused temporarily depending on the situation. Patients should follow individualized instructions from their clinicians, especially for insulin, SGLT2 inhibitors and other drugs affected by dehydration.

The CDC recommends emergency evaluation if a person cannot keep fluids down for more than four hours, has prolonged vomiting or severe diarrhea, develops breathing problems or shows other signs of a hyperglycemic emergency.

Hydration Supports Kidney Health, but It Cannot Undo Diabetes Damage

Diabetes is a leading cause of chronic kidney disease in the United States.

Ongoing high blood sugar can damage the small blood vessels that filter waste from the blood.

Staying hydrated supports normal kidney function and may help prevent complications linked to fluid loss.

But increasing water intake beyond normal needs has not been shown to reverse diabetic kidney disease.

People with diabetes need proper blood sugar and blood pressure control, kidney monitoring and medications when indicated.

Those with advanced kidney disease may need fluid restrictions, which makes individualized medical guidance especially important.