Symptoms of diabetes

Prediabetes and type 2 diabetes can occur without any symptoms. This is especially true in the early stages of the disease. So, it’s important to have regular check-ups, including blood work and other laboratory tests, to screen for health conditions including diabetes.

Regular screening is especially important in a person with a family history of diabetes. For instance, having any first-degree relative (parent, sibling, or child) with type 2 diabetes can increase risk by 2 to 3 times and having both a maternal and paternal history of type 2 diabetes can increase risk by 5 to 6 times. Regular screening is also important if you have other risk factors for diabetes, including if you are overweight and if you are a member of an ethnic group in which diabetes is occurs more frequently (Asian, African, Hispanic, and Native Americans are at increased risk for developing diabetes).1

Symptoms and signs of diabetes

Even though diabetes can develop without symptoms, there are some symptoms that provide clues that a person may have diabetes. These symptoms all results from high blood glucose and include2:

  • Excessive thirst (sometimes called polydipsia)
  • Frequent urination
  • Increased urine production or output (sometimes called polyuria)
  • Unexplained sudden weight loss
  • Constant hunger (polyphagia)
  • Fatigue
  • Sudden changes in vision, including blurred vision
  • Numbness or tingling in the extremities (feet, hands)
  • Sores or cuts that heal slowly or do not heal
  • Frequent infections

Most people who develop type 2 diabetes will not experience the classic symptoms of high blood sugar, which include frequent urination, excessive thirst, urination at night, blurred vision and, in some cases, weight loss. Therefore, measuring excess blood sugar or blood glucose levels is the main way to diagnose diabetes. In most cases, diabetes will be detected during routine laboratory testing as part of a check-up. According to the American Diabetes Association (ADA) diagnostic criteria, diabetes can be diagnosed using a random blood sugar test of 200 mg/dL or higher with symptoms associated with high blood sugar, or on the basis of repeated abnormal readings on either fasting blood glucose, oral glucose tolerance, or hemoglobin A1C tests.3

Diagnosing diabetes: blood sugar testing

Test

Test results

Random blood sugar 200 mg/dL or higher
+ classic symptoms of high blood sugar
Fasting blood glucose* 126 mg/dL or higher**
Oral glucose tolerance† 200 mg/dLor higher**
Hemoglobin A1C 6.5% or higher**

Understanding symptoms

Excessive thirst (polydipsia), frequent urination, and increased urine production. These are classic symptoms of diabetes mellitus, resulting from the effects of high levels of glucose in the blood. Excessive thirst, frequent urination, and increased urine production are signs that the kidney is working overtime to filter high levels of glucose out of the blood.3,4

Learn more about excessive thirst (polydipsia), frequent urination, and increased urine production

Unexplained sudden weight loss, constant hunger (polyphagia), and fatigue. SSudden unexplained weight loss is a classic symptom of type 1 diabetes, resulting from insulin deficiency, with a loss of the hormonal action of insulin in inhibiting the breakdown of protein in the body. Weight loss in type 1 diabetes may also be accompanied by extreme, constant hunger (polyphagia), as well as fatigue, as the body lacks the ability to use glucose. Sudden weight loss is also less frequently a sign of type 2 diabetes, where it may result from dietary restriction on the part of an individual who senses a health problem and deliberately attempts to change eating habits.6,7

Learn more about sudden weight loss, constant hunger (polyphagia), and fatigue.

Sudden changes in vision, including blurred vision. Both type 1 and type 2 diabetes are associated with both short-term and long-term effects on our eyes. Blurred vision is one of the most common symptoms of poorly controlled blood glucose and can affect a person at any stage of diabetes. Blurred vision results from a major change in plasma glucose level, which creates a change in osmotic pressure within the eyeball.3,5

Sudden changes in vision, including blurred vision. Both type 1 and type 2 diabetes are associated with both short-term and long-term effects on our eyes. Blurred vision is one of the most common symptoms of poorly controlled blood glucose and can affect a person at any stage of diabetes. Blurred vision results from a major change in plasma glucose level, which creates a change in osmotic pressure within the eyeball.4,6

Learn more about sudden changes in vision, including blurred vision.

Numbness or tingling in the extremities (feet, hands). Diabetes can have a significant effect on how nerves function. Nerve damage (also called neuropathy) resulting in numbness and tingling in the extremities is a common complication of diabetes. Almost a quarter of people with type 2 diabetes have nerve damage at the time they are diagnosed and up to 50% will eventually develop some type of neuropathy.8,9

Learn more about numbness or tingling in the extremities (feet, hands)

Sores or cuts that heal slowly or do not heal. High blood glucose can cause damage to the small vessels that supply blood to the skin throughout the body. This results in a weakening of the skin, increasing the risk for cuts or wounds and interfering with the body’s ability to heal these injuries. Additionally, poor blood circulation to the extremities (particularly the legs and feet) associated with peripheral vascular disease, which is a common complication of diabetes, can also negatively affect the body’s ability to heal wounds. Common sites of slow healing wounds in people with diabetes including the feet and the gums. 4,10

Learn more about sores or cuts that heal slowly or do not heal

Frequent infections. High blood glucose associated with diabetes can have a negative affect on immune system functions, making the body less able fight infection. Additionally, diabetes-related nerve damage and damage to blood vessels can combined with impaired immunity to work against the body’s ability to detect and fight infection.11

For this reason, people with diabetes tend to develop infections more commonly and these infections tend to be more severe. The main types of infections that occur in people with diabetes include12:

  • Foot infections
  • Urinary tract infections
  • Fungal infections (affecting the mouth, skin and nails)
  • Bacterial infections of the skin and soft tissues
  • Influenza and pneumonia

Learn more about frequent infections.

Written by: Jonathan Simmons | Last reviewed: May 2014.
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