Dr. I-Net
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Diagnosing
Diabetes
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Diagnosing Diabetes:
Type 1 diabetes usually has obvious symptoms, such as frequent urination, increased thirst, and weight loss, type 2 often develops insidiously, showing few or no symptoms. This may explain why it often goes unnoticed at first. On average, people have type 2 diabetes for 9–12 years before they're diagnosed. To reduce this delay, experts now recommend that people ages 45 or older be regularly tested for diabetes.
Recognizing the symptoms Regardless of which type of diabetes you have, the symptoms of high blood sugar, or hyperglycemia, are similar. Symptoms of type 1 diabetes When beta cells stop producing insulin, your body's cells take in less glucose, while your liver releases more, resulting in a dramatic rise in blood sugar levels to as much as 10 times above normal. The excess sugar "spills" into your urine, drawing water with it. This accounts for the frequent urination (polyuria) and insatiable thirst (polydipsia) that can accompany this form of diabetes. It can also lead to dehydration. You may also notice that while your appetite has increased, you've lost weight; this occurs because your cells are literally starved from a lack of nutrients and from the loss of sugar (since each gram of sugar in the urine equals four calories). Dehydration also contributes to weight loss. You may also feel fatigued and irritable, and your vision may be blurry because high sugar levels can change the shape of the lens in your eye and impair its ability to focus.
The start of symptoms in type 1 diabetes is usually abrupt and severe, occurring within days to weeks. Extreme hyperglycemia happens rapidly and leads to dehydration. Insulin deficiency causes other metabolic problems, including the unregulated breakdown of fat stores. This releases fatty acids, which are further broken down to ketones, products of fat digestion that accumulate in the blood. If your ketone concentration gets too high, your blood becomes acidic and diabetic ketoacidosis may occur, sending you into a coma. Fortunately, the condition can usually be averted or treated. Symptoms of type 2 diabetes Because blood sugar levels rise slowly in type 2 diabetes, the symptoms of this more common form of the disease may develop over years or may not occur at all. The early signs and symptoms are the same as for type 1 diabetes: repeated trips to the bathroom, thirst, and fatigue. But they may develop gradually enough to be easily overlooked. Other symptoms can include recurrent urinary infections, tingling or numbness in the hands and feet as a result of nerve damage, and recurring vaginal yeast infections.
Tests for diabetes If you display any of these symptoms or suspect that you might have diabetes, see a doctor promptly. Your doctor will take a full medical history and will probably perform one of three simple blood tests: a random plasma glucose test, a fasting plasma glucose test, or an oral glucose tolerance test. A fourth test, the glycosylated hemoglobin test, is generally used to monitor diabetes after a diagnosis has been made. All these tests require a small blood sample that a lab will analyze for glucose content. Random plasma glucose test The random plasma glucose test measures glucose levels in your blood. If the glucose level exceeds 200 mg/dL, you probably have diabetes, especially if you've noticed symptoms. You don't have to refrain from eating before having this test done, but the glucose content of your meals can affect the results, so it's considered less reliable than the fasting plasma glucose test. Fasting plasma glucose test This test is the current standard for diabetes diagnosis. Like the random plasma glucose test, it measures blood glucose levels, but in this case, blood is drawn after you've refrained from eating for at least eight hours so there isn't any chance of a meal interfering with the results. Normal fasting plasma glucose levels are less than 100 mg/dL, and levels at or above 126 mg/dL indicate diabetes. However, if your first test indicates diabetes, have a second one to confirm the results.
Symptoms of hyperglycemia blurry vision excessive thirst frequent urination feeling very hungry or tired weight loss (without trying) Oral glucose tolerance test Currently, the American Diabetes Association doesn't recommend an oral glucose tolerance test for detecting diabetes. This doesn't reflect any doubts about the test's accuracy. In fact, the oral glucose tolerance test is probably more sensitive than the fasting test. Instead, it's an issue of practicality: The test is considerably more time-consuming and cumbersome than the fasting plasma glucose test. For the oral glucose tolerance test, your glucose level is measured after you've fasted overnight. You drink a sugary solution, and then another blood sample is drawn two hours later. Glucose levels will rise and fall quickly in healthy people. But they rise above normal and decrease slowly in those with diabetes. A person whose glucose level is 200 mg/dL or higher when the second blood sample is drawn has diabetes. This test, like the fasting plasma glucose test, should be repeated on another day to confirm the diagnosis. Glycosylated hemoglobin test Another measurement widely used in diabetes management is the glycosylated hemoglobin test. This blood test reflects the average blood sugar level over the preceding two to three months and will help your doctor monitor your efforts to keep your blood sugar as close to normal as possible. Because having food or a drink before the test won't skew the results, a glycosylated hemoglobin test can be performed at any time of day, even after a meal. Hemoglobin is the oxygen-carrying protein in red blood cells. When glucose in the blood attaches to hemoglobin, the bound product is called HbA1c. (It's also known as glycosylated hemoglobin, glycated hemoglobin, or glycohemoglobin.) Healthy, nondiabetic people usually have an HbA1c level of about 5%, meaning that approximately 5% of their hemoglobin molecules have glucose attached to them. If your diabetes has been well controlled during the previous two to three months, the HbA1c level should be close to normal, that is, less than 7%. If your blood sugar has been high, the level will be elevated. Studies have shown that keeping HbA1c levels low reduces the chances of developing complications of diabetes. It is therefore wise to keep HbA1c levels as close to the nondiabetic range as is safely possible.
The American Diabetes Association advises people with the disease to strive for an HbA1c level of 7% or less Guidelines for diabetes screening The American Diabetes Association (ADA) periodically updates its screening recommendations for diabetes. Because type 1 diabetes usually is diagnosed soon after symptoms develop, the ADA does not recommend widespread screening. The ADA does recommend screening for type 2 diabetes because this form of the disease is more common and may go unrecognized for years. The ADA recommends that everyone age 45 or over be tested for diabetes at least once every three years to ensure earlier diagnosis and intervention before complications develop.
A fasting plasma glucose reading between 100 mg/dL and 126 mg/dL indicates impaired fasting glucose. If this is the case and an oral glucose tolerance test is performed, a two-hour glucose result between 140 mg/dL and 200 mg/dL is considered impaired glucose tolerance. Both conditions raise your risk for diabetes and cardiovascular disease (see "What causes type 2 diabetes?"). To monitor these conditions, it's best to have annual glucose tests.
