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When you eat, your body converts carbohydrates into glucose\u2014a \u201cvital fuel for the body,\u201d says Chhaya Makhija, M.D.<\/a>, endocrinologist at Unified Endocrine and Diabetes Care. That glucose is released into your bloodstream. And insulin helps it move into your cells, where it gets used as energy. But when that final step doesn\u2019t happen, glucose can build up in your bloodstream\u2014causing you to have high blood sugar and experience hyperglycemia symptoms, which may be indicators of diabetes<\/a>.<\/p>\n \u201cHigh blood sugar\u2014also called hyperglycemia\u2014means there\u2019s too much glucose in your bloodstream,\u201d says Lisa Shah, M.D.<\/a>, a physician who specializes in metabolic health. This typically happens because your body doesn\u2019t produce insulin (type 1 diabetes<\/a>), doesn\u2019t produce enough insulin (type 2 diabetes<\/a>), or isn\u2019t able to use insulin effectively (prediabetes and type 2 diabetes), she explains. But you can experience hyperglycemia even if you don\u2019t have diabetes.<\/p>\n Meet the experts: Chhaya Makhija, M.D.<\/a>, CEO, founder, and endocrinologist at Unified Endocrine and Diabetes Care; Lisa Shah, M.D.<\/a>, physician, executive vice president, and chief medical officer at Twin Health<\/a>; Akhil Shenoy, M.D.<\/a>, endocrinologist, internal medicine physician, and medical adviser at Aeroflow Diabetes.<\/p>\n When left untreated, high blood sugar can make you feel tired, weak, and dehydrated\u2014and lead to potentially life-threatening complications<\/a>, like diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS)\u2014more on these below. But you may not experience any symptoms at first, says Akhil Shenoy, M.D.<\/a>, endocrinologist and internal medicine physician. \u201cHyperglycemia doesn\u2019t always feel obvious right away,\u201d Dr. Shah explains. \u201cThe symptoms can be gradual and vague.\u201d<\/p>\n Because of this, experts recommend routine screening<\/a>\u2014especially if you have risk factors for diabetes. Even if you don\u2019t, 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.<\/p>\n High blood sugar symptomsFrequent urination<\/p>\n Constantly running to the toilet? Hyperglycemia may be to blame. \u201cWhen [your] blood sugar is high, your body works hard to bring it back into balance,\u201d Dr. Shah says. Your kidneys go into overdrive trying to flush out that extra sugar. \u201cSince the kidneys cannot simply push out solid sugar cubes, [they] draw water to go along with the sugar, leading to excessive urination<\/a>,\u201d Dr. Shenoy explains.<\/p>\n Increased thirst<\/p>\n Your body is a system. So as your kidneys work to get rid of that extra glucose\u2014and as you start peeing more\u2014you\u2019ll also get thirstier. \u201cThe brain senses high glucose and signals you to drink more water,\u201d Dr. Makhija explains. You might catch yourself reaching for your water bottle more often. You might also experience dehydration symptoms<\/a>, like weakness and dry mouth.<\/p>\n Fatigue<\/p>\n Hyperglycemia can make you feel weak, exhausted, and unlike your usual self. \u201cYou might feel tired, fatigued, or sluggish,\u201d Dr. Shah says. \u201cYou might feel foggy or have a hard time concentrating on something.\u201d In general, you\u2019ll just feel \u201coff,\u201d she explains. And as time goes on, you might notice more obvious high blood sugar symptoms, like increased thirst and urination.<\/p>\n Persistent hunger<\/p>\n When you have high blood sugar, glucose gets \u201cstuck\u201d in your bloodstream, Dr. Shenoy explains. \u201cMeanwhile, the cells of the body\u2014such as the brain, the heart, and the muscle cells\u2014are not receiving the sugar that is needed for normal function,\u201d he says. Your body may try to compensate by going into \u201cstarvation mode,\u201d making you feel hungrier than usual.<\/p>\n Weight loss<\/p>\n High blood sugar can cause rapid, unexplained weight loss<\/a>\u2014for a couple of different reasons. When your body can\u2019t rely on glucose for energy, it starts burning fat and muscle instead, per the Cleveland Clinic<\/a>. \u201cThis is an unhealthy type of weight loss,\u201d Dr. Shenoy explains. Urinating more and dehydration can also contribute to weight loss, Dr. Makhija adds.<\/p>\n Blurry vision<\/p>\n Prolonged high glucose may damage blood vessels<\/a> and nerves throughout the body\u2014including your eyes. The macula (a part of the eye) can swell due to leaky blood vessels (known as macular edema), resulting in blurry vision. While diabetic retinopathy tends to happen after very long periods of high blood sugars, causing leaking blood vessels or new abnormal ones to grow, this tends to lead to blindness. Again, that\u2019s the worst-case scenario, and it often takes a while to occur.<\/p>\n Hyperglycemia may make your vision blurry, simply because it makes you dehydrated. \u201cDehydration affects the eyes, particularly the retinas, which have a rich blood supply,\u201d Dr. Makhija says. When you\u2019re low on fluids, your eyes may get blurry. This is usually a temporary condition. \u201c[But] if sugars remain high for many years, the eye can be permanently damaged,\u201d Dr. Shenoy explains.<\/p>\n Frequent infections<\/p>\n Chronic high blood sugar \u201cimpairs the immune response,\u201d making it harder for your body to fight off infections, Dr. Makhija explains. And being dehydrated all the time certainly doesn\u2019t help, she adds. Because of this, you may find yourself getting sick more often\u2014and staying sick longer than you normally would.<\/p>\n Slow-healing wounds<\/p>\n Since hyperglycemia impacts your immune response<\/a>, 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 \u201creduce awareness of injury and delay healing,\u201d compounding the problem, Dr. Makhija adds.<\/p>\n Fruity breath<\/p>\n Fruity breath isn\u2019t merely a sign of high blood sugar\u2014it\u2019s 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 explains. One of these ketones, acetone, can make your breath smell fruity or metallic\u2014and it\u2019s a warning sign you need to see a doctor ASAP. Untreated DKA can lead to death, so head to the emergency room, stat.<\/p>\n Confusion<\/p>\n High blood sugar can cause fatigue and brain fog<\/a>. But if those symptoms become more severe\u2014and you feel confused, disoriented, or delirious\u2014you may need immediate medical care. These \u201cchanges in mental status\u201d may be symptoms of DKA or hyperosmolar hyperglycemic state (HHS), potentially life-threatening hyperglycemia complications, per Yale Medicine<\/a>.<\/p>\n Upset stomach<\/p>\n Nausea, vomiting, and stomach cramps are warning signs of DKA. When your body can\u2019t rely on glucose for energy, it starts to burn fat and protein\u2014and releases ketones in the process. As those ketones build up in your gastrointestinal tract, they can upset your stomach. \u201cIf you experience nausea, vomiting, abdominal pain, or mental fog, check your ketones and seek urgent care,\u201d Dr. Makhija says. Ketone Sticks<\/a> are over-the-counter test strips that detect ketones in the urine.<\/p>\n High blood sugar complications<\/p>\n Though high blood sugar starts subtly, it can cause serious complications if left untreated. \u201cYou may not feel symptoms in the early stages, but long-term high blood sugar can quietly cause irreversible damage,\u201d Dr. Makhija says.<\/p>\n When glucose builds up in your bloodstream, it can damage your blood vessels\u2014and subsequently your organs and nerves, Dr. Shenoy explains. 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.<\/p>\n Diabetic ketoacidosis (DKA)<\/p>\n Diabetic ketoacidosis (DKA) is a serious complication of high blood sugar that\u2019s especially common in people with type 1 diabetes, explains Dr. Makhija. When your body can\u2019t rely on glucose for energy, it starts breaking down fat and protein instead. \u201cA byproduct of this process is ketones, which are acidic compounds that build up in the blood and make it dangerously acidic,\u201d Dr. Shah says.<\/p>\n Per the Cleveland Clinic<\/a> and Yale Medicine<\/a>, DKA symptoms may include:<\/p>\n Increased thirst or dehydration<\/p>\n Nausea, vomiting, and stomach cramps<\/p>\n When left untreated, DKA may cause a range of dangerous complications, including organ damage, coma, and even death, per the Cleveland Clinic<\/a>. \u201cDKA is a life-threatening emergency and requires urgent treatment,\u201d Dr. Makhija says.<\/p>\n Hyperosmolar hyperglycemic state (HHS)<\/p>\n Hyperosmolar hyperglycemic state (HHS) is another dangerous hyperglycemia complication, but it\u2019s more common among people with type 2 diabetes, Dr. Makhija explains. When your blood sugar stays high for too long, it can cause extreme dehydration and confusion\u2014without the excess ketones you see in DKA, Dr. Shenoy says.<\/p>\n \u201cHHS is similar [to DKA] in that blood sugar is extremely high, but your body produces enough insulin to prevent ketones from building up,\u201d Dr. Shah says. \u201cInstead, 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.\u201d<\/p>\n Per the Cleveland Clinic<\/a> and Yale Medicine<\/a>, HHS symptoms include:<\/p>\n Increased thirst or dehydration<\/p>\n Weakness, especially on one side of the body<\/p>\n The bottom line<\/p>\n