Nancy LeBrun is an Emmy and Peabody award-winning writer and producer who has been writing about health and wellness for more than six years
Kashif J. Piracha, MD, is board-certified in internal medicine and nephrology. He has an active clinical practice at Methodist Willowbrook Hospital in Houston, Texas.
When you're dehydrated, you're losing more fluid than you're taking in, which affects how well your body functions. Dehydration is common in people with diabetes, a chronic condition of high blood sugar. As a result, you may feel extremely thirsty and urinate less frequently, and severe dehydration can be dangerous.
This article will explain the connection between dehydration and diabetes, why it happens, what to do about it, and when it's critical to see a healthcare provider.
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When you’re dehydrated, you lose more fluid through urination or sweat than you get through food or drink. Your body is about 60% water, which keeps many body systems functioning.
If you don't have enough fluid in your body, it's not just that you feel thirsty—it affects your brain, joints, temperature, digestion, and virtually every other system that keeps you going.
If you become severely dehydrated and have diabetes, it can make your blood sugar spike and lead to complications that can be life-threatening. If you feel faint, are not urinating, have a rapid heartbeat or respiration, or feel confused, seek emergency medical care or call 911.
If severe dehydration is not treated, it may lead to seizures, permanent brain damage, or death.
Dehydration is very common in people with diabetes, and extreme thirst, a sign of dehydration, is one of the condition’s three major symptoms. Even if you haven’t been diagnosed, thirst can be an early sign that your blood sugar, or glucose, may be high.
Here's how diabetes can make you prone to dehydration. The kidneys normally reabsorb blood sugar. But if blood sugar levels are too high, the kidneys can't keep up, and sugar passes into the urine, along with more fluid. You pee more. Fluid is also drawn out of cells if you are not drinking enough to keep up. These processes can lead to dehydration.
If you are mildly dehydrated, you may:
People with diabetes are more likely to become dehydrated by:
Everyone needs to drink sufficient amounts of water, but if your blood sugar is high, it makes you urinate more, so you have more fluid to replace. You can get dehydrated if you are not drinking enough water or clear liquid to compensate for the additional fluid loss.
The medical term for excessive thirst is polydipsia, which you feel when your body is signaling you to replace the liquid.
Sweating from intense physical activity makes anyone lose fluid, but if you have diabetes, it can dehydrate you for another reason. While moderate exercise can lower your blood sugar, when you push yourself hard, your muscles can't use insulin (the substance that moves glucose from your bloodstream into your cells) as efficiently.
The glucose remains in your bloodstream because your kidneys can’t keep up. You can develop glycosuria (your urine contains higher than normal amounts of blood sugar).
When the weather is hot and humid, the risk of dehydration rises among everyone, including those with diabetes. The heat makes you lose fluid by sweating.
But when the sweat can't evaporate due to high humidity, your body works harder to stay cool. That means you sweat more, blood circulation increases, you breathe faster, and your body temperature may rise. These factors can reduce the amount of fluid in your body.
Drinking alcohol lowers the amount of a hormone called vasopressin, which suppresses urination. Less vasopressin in your system means you pee more and lose fluid.
The percentage of alcohol in a drink matters. Beer can have a less dehydrating effect than spirits because beer typically has about 5% alcohol, while spirits can be over 50% alcohol.

Expert opinion has evolved on whether caffeine is dehydrating. The idea originated in a 1928 study, which assumed that caffeine is dehydrating because it makes you urinate. However, a 2014 study asserted that drinking moderate amounts of caffeine was not dehydrating.
There is evidence that caffeine consumption may even lower the risk of type 2 diabetes. However, be aware of how much sugar and cream are in your coffee, which can raise your blood sugar.
If you have diabetes and feel symptoms of dehydration, start drinking clear fluids (preferably water) slowly. Other liquids, like sports drinks, can contain a lot of sugar, so water is your best bet.
You will know you are becoming less dehydrated when your urine becomes lighter in color. If you are in the sun, get into the shade or into an air-conditioned building. If you are exercising intensively, slow down and rest while you rehydrate.

Diabetes insipidus is a rare condition in which your body doesn’t regulate fluids the way it should due to hormone imbalance. It shares some symptoms of diabetes mellitus, including extreme thirst and potential dehydration, but it is a different disease.
If you have symptoms of severe dehydration, such as trouble breathing, feeling confused or faint, or feeling like your heart is pounding and you're breathing fast, seek immediate medical care. Severe dehydration can be fatal.
In an emergency setting, healthcare providers can take your vital signs and check your electrolyte (mineral) balance and kidney function. They can address blood sugar levels if they are too high or low and give you fluids through an intravenous (IV) line to reduce dehydration.

Dehydration is a very common symptom of diabetes. Your body is losing more fluid than it's taking in. If your blood sugar is high, your body will work overtime to eliminate it through urination, losing more fluid. Being very thirsty can be an early sign of high blood sugar.
If you feel moderately dehydrated, slowly drink water or clear liquids, and don't exert yourself. If you are in the hot sun, find shade or air conditioning. Severe dehydration can be life-threatening and requires emergency medical care.
Diabetes can be a complex condition, and the higher risk of dehydration is a complicating factor. Your health will benefit from staying well-hydrated.
Talk to a healthcare provider about how many ounces of water you should drink each day if you're not sure. Having a clear goal is good, so you can benefit from consuming plenty of the most important fluid out there.
When you have high blood sugar, your body tries to get rid of it through the kidneys and by pulling water from your cells. That makes you pee more. As a result, you lose fluid, making you feel dehydrated.
If your blood sugar isn't well controlled, you may find you are frequently urinating as your body tries to get rid of the excess blood sugar in your bloodstream.
Yes, dehydration can raise your blood sugar levels because glucose becomes more concentrated when there is less fluid in your body. Sipping water throughout the day and staying away from sugary drinks can help avoid blood sugar spikes.
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By Nancy LeBrun
In addition to her extensive health and wellness writing, Nancy has written about many general interest topics for publications as diverse as Newsweek, Teen Vogue,, and Craftsmanship Quarterly. She has authored a book about documentary filmmaking, a screenplay about a lost civil rights hero, and ghostwritten several memoirs.

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