Doctors Say This Surprising Symptom May Actually Be a Sign of High Blood Sugar

When left untreated, high blood sugar can make you feel tired, weak, and dehydrated—and lead to potentially life-threatening complications, like diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS)—more on these below. But you may not experience any symptoms at first, said Akhil Shenoy, M.D., endocrinologist and internal medicine physician. “Hyperglycemia doesn’t always feel obvious right away,” Dr. Shah explained. “The symptoms can be gradual and vague.”

Because of this, experts recommend routine screening—especially if you have risk factors for diabetes. Even if you don’t, you should keep an eye out for the following high blood sugar symptoms and get to a doctor if you experience several of them at once.

Frequent urination

Constantly running to the toilet? Hyperglycemia may be to blame. “When [your] blood sugar is high, your body works hard to bring it back into balance,” Dr. Shah said. Your kidneys go into overdrive trying to flush out that extra sugar. “Since the kidneys cannot simply push out solid sugar cubes, [they] draw water to go along with the sugar, leading to excessive urination,” Dr. Shenoy explained.

Increased thirst

Your body is a system. So as your kidneys work to get rid of that extra glucose—and as you start peeing more—you’ll also get thirstier. “The brain senses high glucose and signals you to drink more water,” explained Chhaya Makhija, M.D., endocrinologist at Unified Endocrine and Diabetes Care. You might catch yourself reaching for your water bottle more often. You might also experience dehydration symptoms, like weakness and dry mouth.

Fatigue

Hyperglycemia can make you feel weak, exhausted, and unlike your usual self. “You might feel tired, fatigued, or sluggish,” Dr. Shah said. “You might feel foggy or have a hard time concentrating on something.” In general, you’ll just feel “off,” she explained. It’s important to note that fatigue is a sign of numerous possible health conditions, so if you’re just feeling tired and foggy, it’s unlikely that your blood sugar is to blame. But if you experience fatigue coupled with other high blood sugar symptoms, that could be a clue.

Persistent hunger

When you have high blood sugar, glucose gets “stuck” in your bloodstream, Dr. Shenoy explained. “Meanwhile, the cells of the body—such as the brain, the heart, and the muscle cells—are not receiving the sugar that is needed for normal function,” he said. Your body may try to compensate by going into “starvation mode,” making you feel hungrier than usual, even shortly after eating.

Weight loss

High blood sugar can cause rapid, unexplained weight loss—for a couple of different reasons. When your body can’t rely on glucose for energy, it starts burning fat and muscle instead, per the Cleveland Clinic. “This is an unhealthy type of weight loss,” Dr. Shenoy noted. Urinating more and dehydration can also contribute to weight loss, Dr. Makhija added.

Blurry vision

Prolonged high glucose may damage blood vessels and nerves throughout the body—including your eyes, according to Johns Hopkins Medicine. The macula (a part of the eye) can swell due to leaky blood vessels (known as macular edema), resulting in blurry vision. Diabetic retinopathy can occur after very long periods of high blood sugars; this causes your blood vessels to leak or new abnormal ones to grow and tends to lead to blindness. However, that’s the worst-case scenario, and it often takes a while to occur.

Hyperglycemia may make your vision blurry, simply because it makes you dehydrated. “Dehydration affects the eyes, particularly the retinas, which have a rich blood supply,” Dr. Makhija said. When you’re low on fluids, your eyes may get blurry. This is usually a temporary condition. “[But] if sugars remain high for many years, the eye can be permanently damaged,” Dr. Shenoy explained.

Frequent infections

Chronic high blood sugar “impairs the immune response,” making it harder for your body to fight off infections, Dr. Makhija explained. And being dehydrated all the time certainly doesn’t help, she added. Because of this, you may find yourself getting sick more often—and staying sick longer than you normally would.

Slow-healing wounds

Since hyperglycemia impacts your immune response, it can also make it harder for your body to heal cuts and bruises. Chronic high blood sugar can also cause poor circulation and nerve damage, which can “reduce awareness of injury and delay healing,” compounding the problem, Dr. Makhija added.

Fruity breath

Fruity breath isn’t merely a sign of high blood sugar—it’s a symptom of diabetic ketoacidosis (DKA), a dangerous hyperglycemia complication. When your body starts burning protein and fat for energy, it releases ketones, Dr. Makhija explained. One of these ketones, acetone, can make your breath smell fruity or metallic—and it’s a warning sign you need to see a doctor ASAP. Untreated DKA can lead to death, so head to the emergency room, stat.

Confusion

High blood sugar can cause fatigue and brain fog. But if those symptoms become more severe—and you feel confused, disoriented, or delirious—you may need immediate medical care. These “changes in mental status” may be symptoms of DKA or hyperosmolar hyperglycemic state (HHS), potentially life-threatening hyperglycemia complications, per Yale Medicine.

Upset stomach

Nausea, vomiting, and stomach cramps are warning signs of DKA. When your body can’t rely on glucose for energy, it starts to burn fat and protein—and releases ketones in the process. As those ketones build up in your gastrointestinal tract, they can upset your stomach. “If you experience nausea, vomiting, abdominal pain, or mental fog, check your ketones and seek urgent care,” Dr. Makhija said. Again, GI symptoms can have a variety of different causes. But if you are experiencing them alongside other signs on this list, it may be worth picking up some over-the-counter test strips from the drugstore that can measure ketones in the urine.

Though high blood sugar starts subtly, it can cause serious complications if left untreated. “You may not feel symptoms in the early stages, but long-term high blood sugar can quietly cause irreversible damage,” Dr. Makhija said.

When glucose builds up in your bloodstream, it can damage your blood vessels—and subsequently your organs and nerves, Dr. Shenoy explained. Chronic high blood sugar can also lead to diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS), two serious complications that can cause coma, organ damage, and death in severe cases.

Diabetic ketoacidosis (DKA)

Diabetic ketoacidosis (DKA) is a serious complication of high blood sugar that’s especially common in people with type 1 diabetes, explained Dr. Makhija. When your body can’t rely on glucose for energy, it starts breaking down fat and protein instead. “A byproduct of this process is ketones, which are acidic compounds that build up in the blood and make it dangerously acidic,” Dr. Shah said.

Per the Cleveland Clinic and Yale Medicine, DKA can cause many of the symptoms above—but others that are unique to this complication include rapid heart rate, shortness of breath, and fainting.

When left untreated, DKA may cause a range of dangerous complications, including organ damage, coma, and even death, per the Cleveland Clinic. “DKA is a life-threatening emergency and requires urgent treatment,” Dr. Makhija said.

Hyperosmolar hyperglycemic state (HHS)

Hyperosmolar hyperglycemic state (HHS) is another dangerous hyperglycemia complication, but it’s more common among people with type 2 diabetes, Dr. Makhija explained. When your blood sugar stays high for too long, it can cause extreme dehydration and confusion—without the excess ketones you see in DKA, Dr. Shenoy said.

“HHS is similar [to DKA] in that blood sugar is extremely high, but your body produces enough insulin to prevent ketones from building up,” Dr. Shah said. “Instead, the problem is that the excess sugar makes your blood very concentrated. Your body then tries to dilute it by pulling water from elsewhere into the bloodstream, which exacerbates dehydration and throws off electrolyte balance.”

Per the Cleveland Clinic and Yale Medicine, HHS symptoms also look similar to those of high blood sugar, typically including things like frequent urination, increased thirst, blurry vision, and confusion. In addition, HHS can cause weakness, especially one side of the body, fainting, and coma.

A routine blood test (or even a finger prick) can give your doctor insight into your levels. The good news: When caught early, there are many medications available (from Ozempic to full-on insulin) to help manage blood sugars. If you have the symptoms on this list or are simply concerned that your blood sugar is high, ask your healthcare provider about next steps. If you believe you are experiencing DKA or HHS, seek immediate treatment. In severe cases, these conditions may cause seizures, organ damage, coma, and death. “If symptoms escalate or you’re unsure, call 911 or go to the emergency room,” Dr. Makhija said. “DKA and HHS are not manageable at home.”