What Happens to Blood Sugar When You Do Not Drink Enough Water?

How Does Insufficient Water Intake Affect Blood Sugar?

Prevent Dehydration

Insufficient water intake can lead to dehydration, reducing the water content in the blood and raising blood sugar levels, as well as increasing the burden on the kidneys. Adequate water intake is beneficial for diabetes patients in managing their blood sugar levels, and choosing drinking water instead of sugary beverages can reduce carbohydrate and calorie intake. Dehydration can cause an increase in blood sugar levels, and high blood sugar can prompt the kidneys to excrete excess glucose through urine. Increasing urine output leads to more water loss. High temperatures, fever, vomiting, and diarrhea can further increase the risk of dehydration. Elderly people may have weakened thirst sensation as they age, and are more likely to experience insufficient water intake. 

Blood Sugar Control

Water contains no carbohydrates or calories, so drinking water can serve as an auxiliary measure for diabetes management. Adequate hydration helps correct dehydration and assist in blood sugar management. However, if blood sugar remains persistently high, it is still necessary to pay attention to medication use, diet, disease conditions and personal treatment plans. Distributing water intake evenly throughout the day helps maintain fluid balance. Diabetic patients should monitor their blood sugar more frequently according to the doctor's advice when they are ill or in extremely hot weather to detect abnormalities in a timely manner.

Kidney Function

The kidneys rely on adequate blood flow to filter waste and regulate fluid and electrolyte levels. Severe dehydration reduces the blood supply to the kidneys, increasing the risk of acute kidney injury, especially when one is ill or losing a large amount of body fluids. Long-term high blood sugar also damages the filtering structure of the kidneys and increases the risk of diabetic kidney disease. Therefore, maintaining an appropriate intake of water helps to maintain normal kidney function, but blood sugar control, blood pressure management, and regular kidney function tests remain important components of diabetes management. For diabetic patients who also have advanced kidney disease, heart failure or are undergoing dialysis treatment, their water requirements should be evaluated based on individual circumstances, as some patients need to limit their fluid intake.

Weight Management

Water intake helps with weight management because the intake of carbohydrates and calories is reduced by replacing sugary and high-calorie beverages with plain water. Sugary sodas, fruit drinks, and sweetened teas not only cause blood sugar levels to rise but also increase daily energy intake. Having a ready supply of water during meals and daily activities helps to develop a regular drinking habit. Pure carbonated water and unsweetened water flavored with cucumbers or citrus fruits are also good choices. Continuous weight management requires a comprehensive diet and exercise plan, and maintaining adequate water intake is one of the simple and practical measures.

Why Are Diabetics More Prone to Dehydration?

High Blood Sugar and Frequent Urination

Diabetic patients are more prone to dehydration, mainly because high blood sugar leads to increased water loss in urine. Fever and hot weather also increase the body's demand for water. Certain diabetes medications and diuretics may also exacerbate water loss. When blood sugar rises above the kidneys' ability to reabsorb glucose, the excess glucose will enter the urine and carry away more water. This process is called osmotic diuresis, which can lead to frequent urination, increased thirst, and even multiple awakenings at night to use the toilet. When patients are unwell or unable to drink water in time, the risk of dehydration increases further.

Fever and Hot Weather

Fever can increase the loss of body fluids through the skin and breathing. The stress hormone response triggered by infection may cause an increase in blood sugar, which further aggravates the increased urine loss due to high blood sugar. High-temperature weather also promotes sweating, especially during exercise or outdoor work, making the risk of dehydration even higher. Diabetes-related nerve damage may interfere with normal sweating and temperature regulation functions, thereby increasing the risk of overheating. During illness or in high-temperature weather, diabetic patients should monitor their blood sugar levels more frequently according to their personal care plan. Symptoms such as darker urine color, reduced urine output, dizziness, and dry mouth may indicate dehydration, and it is necessary to promptly assess water intake.

Some Medications

SGLT2 inhibitors, such as empagliflozin and dapagliflozin, lower blood sugar by promoting the kidneys to excrete more glucose into the urine. At the same time, water is also expelled, leading to increased urination and an increased risk of dehydration, especially when one is ill or exposed to high temperatures. Diuretics used to treat conditions like hypertension and heart failure also increase the excretion of salt and water. If used together with SGLT2 inhibitors, the risk of fluid loss may further increase. Metformin and GLP-1 receptor agonists may cause vomiting or diarrhea, resulting in water and electrolyte loss.

How to Manage Blood Sugar Through Proper Hydration?

Regular Water Intake

It is recommended to drink an appropriate amount of water during meals, between meals and after exercise in daily life. Also, carry a reusable water bottle with you to develop the habit of drinking water regularly. The amount of water needed per day varies depending on activity level, weather conditions, and overall health status. Therefore, it is not advisable to use a fixed standard of water intake that applies to everyone. Light yellow urine can be a general reference for judging the water status, but certain medications and dietary supplements may also affect the color of urine.

Replacing Beverages With Water, Unsweetened Tea or Unsweetened Sparkling Water

Water contains no carbohydrates or calories. Therefore, replacing regular soda, sugary tea, energy drinks and sugary coffee beverages with water is a simple way to manage blood sugar in daily life. For those who enjoy flavors or the effervescence, sugar-free tea and sugar-free soda water are also good alternatives. However, it is important to carefully check the product labels as some so-called healthy flavored beverages may still contain sugar, fruit juice concentrate, or syrup. Lemon slices, cucumber slices, or mint leaves can add flavor to plain water without significantly increasing carbohydrate intake.

Consuming Foods Rich in Water

Cucumbers, lettuce, tomatoes and oranges all contain a relatively high amount of water. Among them, cucumbers, lettuce and tomatoes have a lower carbohydrate content at common serving sizes and are suitable to be incorporated into daily diets through salads, sliced vegetables or tomato-based side dishes. For those who need to control their carbohydrate intake or adjust their insulin dosage during meals, they should pay attention to the portion size when eating oranges, as a medium-sized orange usually contains about 15 grams of carbohydrates. Compared to orange juice, a whole orange contains dietary fiber and is more helpful in increasing satiety.

Monitoring Blood Sugar

Patients should be monitored according to the monitoring plan established by the doctor, and pay attention to abnormal blood glucose readings in combination with dietary intake, medication use, activity level, and water loss. If blood sugar remains persistently high, they should adhere to the established blood sugar correction plan or daily management plan, replenish water appropriately to maintain fluid balance, and use medication as prescribed to regulate blood sugar. If the care plan requires the detection of ketone bodies, patients should undergo the test when they reach the specified blood glucose threshold or during the illness period. This is particularly important for patients with type 1 diabetes. If symptoms such as vomiting, abdominal pain, deep breathing or rapid breathing, confusion, or inability to replenish and retain fluids occur, immediate medical assistance should be sought, even if the blood sugar reading does not significantly exceed the expected range.