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Diabetes: Types, Symptoms & Diagnosis

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Diabetes is a metabolic disease marked by high blood glucose, also known as blood sugar.

There are three types of diabetes: type 1 diabetes, type 2 diabetes and gestational diabetes. In all three cases, the pancreas either does not produce enough insulin, a hormone that regulates blood sugar, or the body's cells fail to respond to insulin's signals. Symptoms include frequent thirst and urination, fatigue and blurry vision and numbness in the hands and feet. About 26 million Americans have diabetes, according to a 2011 Centers for Disease Control and Prevention report.

Complications from diabetes include damage to the body tissues, including the heart and blood vessels. Two-thirds of people with diabetes will die of heart disease or stroke, according to the American Diabetes Association (ADA).

Diabetes also carries a risk of skin problems that end with amputation. The tissue damage caused by diabetes can lead to peripheral arterial disease, which reduces circulation to the extremities. Poor circulation, in turn, makes infection more likely. Compounding the problem, nerve damage, or diabetic neuropathy, makes it hard for people with diabetes to notice injuries, blisters or ulcers, particularly on the feet. Thus, people with diabetes must take proper care of their feet and pay close attention to potential problems.

Types of diabetes

Diabetes comes in three types. The first, type 1 diabetes, was once known as "juvenile diabetes" or "insulin-dependent diabetes mellitus."

Type 1 diabetes is an autoimmune disorder. The body's immune system attacks the islet cells of the pancreas, which produce the blood-sugar-regulating hormone insulin. As a result, the pancreas stops producing insulin, or does not produce enough for the body's needs. About 5 percent of diabetes cases are Type 1 diabetes, which is usually diagnosed in childhood.

Type 2 diabetes is the most common type of diabetes. In type 2 diabetes, the pancreas produces insulin without a problem, but the body's cells fail to respond to the hormone. This failure to respond is called insulin resistance.

Researchers have yet to pinpoint why some people develop insulin resistance and others don't. Obesity and inactivity are contributing factors, however. A gene passed to Homo sapiens from the extinct human Neanderthals might confer extra type 2 diabetes risk, according to research released in 2014.

The third type of diabetes is gestational diabetes. Like type 2 diabetes, this form of the disease occurs when the body's cells fail to respond to insulin. Gestational diabetes starts during pregnancy. Sometimes it vanishes after pregnancy; other times, the condition is chronic.

Diagnosis and treatment

There are three tests for diabetes. The first is that A1C blood test, which measures average blood glucose over the past three months. The test measures glucose attached to hemoglobin, the oxygen-carrying protein in blood. The red blood cells that carry this protein live about three months, so measuring them at a single time point gives a history of the amount of glucose in the blood. An abnormal A1C test will return levels above 5.7 percent.

A second test, the fasting plasma glucose test, requires the patient to fast for eight hours before having a blood glucose test. This test reveals how effectively the body metabolizes glucose. More than 126 milligrams of glucose per deciliter (mg/dl) of blood signals diabetes.

The final test, the oral glucose tolerance test, is often used for gestational diabetes screening. This test requires the patient to drink an extra-sugary drink. Two hours later, the person undergoes a blood test. More than 200 mg/dl of glucose in the blood is a red flag for diabetes.

The treatment for type 1 diabetes is regular insulin injections, sometimes delivered with an insulin pump, a catheter device that automatically dispenses the hormone.

Type 2 diabetes may require insulin injections, but is often treatable with diet, exercise and other drugs such as metformin.

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Stephanie Pappas

Stephanie interned as a science writer at Stanford University Medical School, and also interned at ScienceNow magazine and The Santa Cruz Sentinel. She has a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science writing from the University of California, Santa Cruz. To find out what her latest project is, you can follow Stephanie on .
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