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Increased thirst.
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Frequent urination, including at night.
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Blurred vision.
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Increased hunger.
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Unexplained weight loss.
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Recurrent infections.
Not everyone experiences these symptoms, and type 2 diabetes can remain undetected for years.
When should fatigue be investigated?
Consider a medical assessment if fatigue is persistent, unexplained, or affecting your ability to work, exercise, or complete ordinary activities.
Depending on your symptoms and medical history, a clinician may recommend blood glucose testing, a blood count, thyroid tests, or other investigations.
Severe fatigue accompanied by vomiting, abdominal pain, rapid or deep breathing, confusion, or marked dehydration may indicate a medical emergency, particularly in someone with undiagnosed or poorly controlled diabetes.
6. Other Diabetes Warning Signs Worth Recognizing
The five symptoms discussed above are not the only signs to consider. Several more familiar symptoms are particularly important because they can occur when blood glucose becomes substantially elevated.
Increased thirst and frequent urination
When blood glucose is very high, the kidneys may begin to excrete excess glucose into the urine. Water follows the glucose, increasing urine production and potentially causing dehydration.
A person may therefore urinate more often and feel unusually thirsty. Nighttime urination may become more noticeable.
These symptoms can also occur with other conditions, but their combination deserves medical assessment.
Blurred vision
Changes in blood glucose can alter fluid balance in the eye's lens, temporarily affecting vision. Over time, diabetes can also damage the blood vessels in the retina, leading to diabetic retinopathy.
Sudden vision loss or a sudden change in vision requires urgent medical evaluation rather than waiting to see whether it improves.
Unexplained weight loss
Some people with uncontrolled diabetes lose weight even when they are eating normally or feeling unusually hungry. This can occur because the body cannot use glucose effectively and begins relying more heavily on other energy sources.
Unintentional weight loss should always be investigated, particularly when accompanied by thirst, frequent urination, or fatigue.
Increased hunger
Changes in insulin function can affect how the body uses energy. Some people experience increased hunger despite consuming enough food.
Hunger is common and can have many explanations, but persistent hunger combined with other diabetes symptoms is worth discussing with a clinician.
7. How Is Diabetes Diagnosed?
Recognizing symptoms is useful, but a blood test—not a symptom checklist—is needed to diagnose diabetes.
Several tests may be used, depending on the circumstances.
A1C test
The A1C test estimates average blood glucose over approximately the previous two to three months.
Common diagnostic thresholds for nonpregnant adults are:
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Below 5.7%: generally considered within the normal range.
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5.7% to 6.4%: the range used to identify prediabetes.
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6.5% or higher: the diabetes range.
A clinician may need to repeat an abnormal result to confirm the diagnosis, unless the clinical situation clearly establishes diabetes. Certain conditions, including some forms of anemia and disorders affecting red blood cells, can influence A1C accuracy.
Fasting plasma glucose
This test measures blood glucose after fasting for at least eight hours.
For nonpregnant adults, the commonly used thresholds are:
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Below 100 mg/dL (5.6 mmol/L): generally normal.
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100–125 mg/dL (5.6–6.9 mmol/L): the prediabetes range.
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126 mg/dL (7.0 mmol/L) or higher: the diabetes range.
An abnormal result usually requires confirmation unless there is clear evidence of diabetes.
Oral glucose tolerance test
This test measures the body's response to a standardized glucose drink. Blood glucose is checked before and after the drink at specified intervals.
It is particularly useful in certain diagnostic situations and is also used in screening for gestational diabetes, although pregnancy-specific criteria differ.
Random plasma glucose
A random blood glucose test can help diagnose diabetes when a person has classic symptoms of high blood sugar. A result of 200 mg/dL (11.1 mmol/L) or higher may meet the diagnostic criterion when accompanied by classic symptoms of hyperglycemia or a hyperglycemic crisis.
The interpretation depends on the clinical circumstances, and a healthcare professional should determine whether additional testing is required.
These thresholds are widely used diagnostic criteria, but the appropriate testing pathway may vary according to pregnancy, age, other medical conditions, and local guidelines.
8. Who Should Consider Diabetes Screening?
Symptoms are not the only reason to check blood glucose. Some people should be screened because their risk is elevated even when they feel perfectly healthy.
Risk factors for type 2 diabetes include excess body weight, physical inactivity, a family history of diabetes, previous gestational diabetes, and certain metabolic conditions.
Risk also increases with age, although type 2 diabetes can develop in younger adults and children.
People with high blood pressure, abnormal cholesterol or triglyceride levels, cardiovascular disease, or a history of polycystic ovary syndrome may also benefit from discussing screening with a healthcare professional.
The recommended age and frequency of screening depend on the person's risk factors and the guidelines followed in their country.
Importantly, people should not wait for symptoms if they already meet screening criteria. Type 2 diabetes can develop gradually, and early testing may identify the condition before noticeable complications arise.
9. What Can You Do to Reduce the Risk of Type 2 Diabetes?
Not every case of diabetes can be prevented. Type 1 diabetes, for example, has a different underlying mechanism from type 2 diabetes and is not caused simply by eating too much sugar.