Symptoms of high blood sugar

According to the American Diabetes Association (ADA), in people with type 2 diabetes, hyperglycemia (high blood sugar) usually develops gradually and, in the early stages, is usually not severe enough for you to notice any typical symptoms. This may be why many people go undiagnosed for years, but being able to recognize the symptoms of high blood sugar can help you diagnose diabetes, better manage it, and prevent emergencies.

For those who have already been diagnosed with diabetes, the occasional higher-than-usual blood sugar doesn’t necessarily put you at immediate risk. However, chronically elevated blood sugar can be problematic. Over time, high blood sugar levels can affect the body’s large and small blood vessels, leading to complications in the eyes, heart, kidneys, and feet.

common symptoms

For the undiagnosed, the common symptoms of high blood sugar can be a warning sign of diabetes. If you know you have diabetes, noticing these symptoms may indicate that you need to adjust your treatment plan.

Excessive thirst (polydipsia)

To restore blood sugar balance, your body tries to excrete excess sugar through urine. As a result, the kidneys are forced to work overtime to absorb the excess sugar. However, because they can’t keep up with the glucose load, they’ll draw fluid, along with excess sugar, from your tissues.

The more fluid you lose, the stronger your urge to drink. If you find that you can drink continuously but feel your thirst is not getting better, or you have severe dry mouth, this may be a sign of hyperglycemia.

Increased hunger (eating more)

Too much sugar in your blood means your body can’t use it for fuel. As a result, your cells become starved of energy, and you feel extra hungry and, in extreme cases, insatiable. But the more carbohydrates you eat, the higher your blood sugar.

Increased urination (polyuria)

Going to the bathroom more often, especially at night, can be a sign of high blood sugar. This is due to the kidneys pumping excess water out of your tissues to dilute excess sugar in your blood and excrete it in your urine.

blurred vision

High sugar levels force the body to pump fluid from your tissues, including the lens of your eye, which can affect your concentration and cause blurred vision.

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When sugar stays in your blood instead of being carried to your cells for energy, your cells become starved of food, leaving you feeling sluggish or fatigued. This usually happens after you eat a meal, especially one that is high in carbohydrates.

severe symptoms

These specific symptoms tend to occur when someone has chronic hyperglycemia or extremely elevated blood sugar. They usually indicate an emergency.


Chronic high blood sugar can lead to nerve damage in the stomach (gastroparesis). Stomach pain can also be a sign of diabetic ketoacidosis, a medical emergency that requires immediate treatment.

lose weight

Unintentional weight loss is an important sign, especially in children who drink and urinate regularly, with elevated blood sugar. Many children diagnosed with type 1 diabetes lose weight before diagnosis. This is usually because the body cannot use the sugar in the blood for fuel.

Changes in mouth and breathing

Nausea, vomiting, fruity breathing, deep and short breathing, and loss of consciousness are signs that you need emergency help. These symptoms can be warning signs of other diabetes-related conditions that can lead to death if not treated right away.

rare symptoms

People with high blood sugar may also experience some rarer symptoms.


Damage to the nerves in the extremities (called peripheral neuropathy) occurs over time and may manifest as numbness, tingling, or pain in the hands, feet, or legs.

skin condition

Dry/itchy skin, slow-healing cuts or wounds, and acanthosis nigricans (thick, velvety patches found in folds or creases in areas like the neck, indicating insulin resistance) can be signs of hyperglycemia.

frequent yeast infections and erectile dysfunction

These manifestations can affect women and men separately.

hyperglycemic hyperosmolar nonketotic syndrome

Hyperglycemic hyperosmolar nonketotic coma (HHNKC) is an extremely serious complication that can occur in people with type 1 or type 2 diabetes, but is most common in non-insulin dependent patients (type 2 diabetes).

HHNKC is characterized by dangerously high blood sugar above 600 mg/dL, usually caused by infections such as pneumonia, urinary tract infections, or inability to effectively control blood sugar. If left untreated, it can lead to coma or even death.

Signs and symptoms include:

  • extremely thirsty
  • Puzzled
  • Fever (usually over 101 degrees)
  • Weakness or paralysis on one side of the body

The best way to prevent HHNKC is to take your medication as directed and to keep in touch with your healthcare team if your blood sugar continues to exceed 300 mg/dL.

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diabetic ketoacidosis

High blood sugar can lead to another very dangerous condition called diabetic ketoacidosis (DKA), which is most common in people with type 1 diabetes and is often the condition that leads to a diagnosis of type 1 diabetes.

DKA is caused when the body uses little or no insulin, and as a result, blood sugar rises to dangerous levels and the blood becomes acidic. Cellular damage may occur and, if it continues to worsen, may lead to coma or death. DKA requires immediate medical intervention— Patients with DKA need to be monitored by a medical professional and given intravenous fluids, electrolytes, and insulin.


Frequent and prolonged hyperglycemia can lead to a series of complications called micro (small) and macro (macro) blood vessel problems. They include damage to:

  • eye (retinopathy)
  • Kidneys (nephropathy)
  • Peripheral and autonomic neuropathy (loss of nerves in the feet and other parts of the body, such as the gut)

Additionally, chronically elevated blood sugar can cause or exacerbate heart disease and peripheral arterial disease.

pregnancy period

High blood sugar during pregnancy is especially harmful to the mother and unborn child. According to the ADA, uncontrolled gestational diabetes carries risks such as spontaneous miscarriage, fetal abnormalities, preeclampsia (uncontrolled blood pressure in the mother), fetal death, macrosomia (large babies), low blood sugar in the baby at birth, and Neonatal hyperbilirubinemia. In addition, gestational diabetes may increase the risk of obesity and type 2 diabetes in offspring.

The ADA guidelines for women with diabetes emphasize the importance of preconception counseling. It should emphasize the importance of achieving near-normal blood glucose levels as safely as possible – ideally A1C <6.5% (48 mmol/mol) - to reduce the risk of congenital anomalies, preeclampsia, macrosomia and other complications risk.

in children

Hyperglycemia in children, especially if undiagnosed, can lead children with type 1 diabetes to develop type 2 diabetes or ketoacidosis. Those children with diabetes who have chronically elevated blood sugar levels are at increased risk of developing diabetes complications.

When to see a healthcare provider

If you don’t feel like your usual self and think your blood sugar is elevated, get a test to confirm. If your blood sugar happens to be elevated and it’s an isolated event, you’ll most likely be able to get back to normal on your own. Go for a walk or do some light exercise, drink plenty of fluids, and take your medication as prescribed.

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On the other hand, if you have elevated blood sugar for several days in a row, call your healthcare team as you may need to adjust your treatment plan.

If you do not have diabetes and notice any of these signs or symptoms, and are overweight or obese or have a family history of diabetes, you should make an appointment with your healthcare provider for a screening. Both macrovascular and microvascular complications of diabetes can occur before diagnosis, so the sooner you get treatment, the better.

If you notice your child is drinking, eating, and urinating more often than usual, it’s a good idea to see a healthcare provider, especially if you’re seeing rapid weight changes. If symptoms seem more severe and similar to DKA (see above), go to the emergency room right away.

If your child has symptoms of hyperglycemia and their blood sugar is above 240 mg/dL, they should be tested for ketones. If the test comes back positive, depending on the severity of the ketone bodies, you may be referred to the emergency room.

Frequently Asked Questions

  • Are the symptoms of non-diabetic hyperglycemia and diabetic hyperglycemia the same?

    They are very similar. Both diabetic and non-diabetic hyperglycemia can cause:

    • excessive thirst
    • frequent urination
    • blurred vision
    • nausea and vomiting
    • fatigue

    People with diabetes may also feel excessively hungry, and untreated diabetic hyperglycemia may lead to more severe symptoms.

  • What are the signs that you have ketoacidosis?

    In the early stages, the symptoms of ketoacidosis are like the symptoms of hyperglycemia: excessive thirst, frequent urination, and high blood sugar. As the condition progresses, you may experience extreme hunger from unexpected weight loss, fatigue and confusion, difficulty breathing, and dry skin.

  • Does being constantly hungry mean I have diabetes?

    maybe. If you have other symptoms, especially increased thirst and need to urinate, you should check your blood sugar. However, other conditions can also cause intense hunger, called polyphagia, including thyroid disease, mood disorders, and hormonal fluctuations.

How is hyperglycemia diagnosed?