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THREE. How Do I Know I Have Diabetes?

How does my doctor confirm the diagnosis of diabetes?

My doctor says I have hypoglycemia. Isn't that the opposite of diabetes?

I have a strong family history of diabetes. How often should I be checked for it?


What are the most common symptoms of diabetes?

The common and early symptoms of diabetes result from the effect of the high blood sugar entering the urine and drawing fluid from the body's tissues along with it. This leads to excess urine production with frequent urination. The loss of body fluid leads to thirst, in order to replace the fluid loss. As long as the person with diabetes is able to keep pace with his or her thirst by regular fluid intake, he or she will remain relatively well. However, without free access to fluid, which can occur for a variety of reasons, one will become dehydrated, which leads to dizziness upon standing upright drowsiness, confusion, and ultimately fainting and unconsciousness. Due to the wasting of calories as glucose in the urine, patients will complain of hunger and will usually lose weight if high blood sugar is very marked. However, it is important to note that only a minority of people with diabetes will experience these symptoms. Frequently, the degree of high blood sugar is more moderate, with little sugar entering the urine and causing no immediate symptoms. However, diabetes of even modest severity can cause considerable harm and lead to serious chronic complications. Therefore, it is important to detect diabetes that is asymptomatic (i.e., without symptoms), which is the reason that screening programs to detect diabetes in those at highest risk have been developed. If asymptomatic diabetes is not discovered for a sufficiently long period (many months or years), patients may actually present with long-term complications of the previously unrecognized diabetes, such as heart attack, stroke, heart failure, neuropathy (nerve damage), nephropathy (kidney damage), or retinopathy (eye damage). These are discussed in Questions 32 to 35.


Having no complaints or symptoms.

How does my doctor confirm the diagnosis of diabetes?

Your doctor will perform one of the standard measurements for the diagnosis of diabetes approved by the accepted authoritative body in whichever part of the world you live. In the United States, this is generally set by the American Diabetes Association (ADA) and is accepted by most practitioners, insurers, and health providers as valid. The most current ADA criteria for the diagnosis of diabetes are shown in Table 1 (see Question 9). Your doctor may or may not ask you to fast prior to measuring the blood glucose or he or she may perform a standard 2-hour test known as the oral glucose tolerance test. Unless they are clearly and indisputably abnormal, or accompanied by typical symptoms of diabetes (discussed in Question 4), the results should be confirmed on a different day, since the diagnosis of diabetes carries many implications and necessitates lifelong monitoring and treatment. Very soon, the test that measures the average blood glucose over the past 3 months (the Hemoglobin Alc or HbAlc test) is also likely to become a standard test for detection and diagnosis of diabetes.

Different diagnostic procedures are used for pregnant women, most of whom should be screened for the presence of diabetes of pregnancy ("gestational diabetes") during the 24th to 28th week of pregnancy or earlier if they are at high risk or had diabetes in a previous pregnancy. This involves an initial 1-hour screening test for which fasting is not required. If the screening test is positive, it is followed by a more detailed 3-hour test for which prior fasting is necessary.

Although many people with diabetes confidently state that they can reliably detect both their high and low blood sugars without actual measurement, studies have shown that these beliefs are not usually accurate.


An abnormally low level of glucose in the blood; symptoms include shakiness, sweatiness, hunger, abdominal discomfort, palpitations, and confusion.


An abnormally high level of glucose in the blood; secondary symptoms include frequent urination and thirst.

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