raises blood glucose by stimulating the liver to release stored glucose.
We’ve only just recently begun to understand the delicate and complicated process of insulin and glucagon secretion. Together, these processes work to maintain a steady level of glucose in the blood all the time. This process is central to understanding how diabetes develops and how to treat it.
People have known about diabetes since antiquity. Unfortunately, for thousands of years, they didn’t know how it worked or how to treat it. Beginning in the Enlightenment (17th and 18th centuries), this began to change.
Early Glucose Discoveries
• In 1776, scientists discovered that glucose was in the blood of both people with and people without diabetes. That led them to suspect that people with diabetes pass glucose from blood into urine. But they didn’t know how.
• Over one hundred years later, in 1889, two German physiologists, Oskar Minkowski and Joseph von Mering, accidently discovered that the pancreas is involved in diabetes. As part of their experiments on how the body uses fat, they removed the pancreas of a laboratory dog. Much to their astonishment, the dog urinated again and again. Luckily, the scientists tested the dog’s urine for glucose. Sure enough, the dog had developed diabetes when its pancreas was removed. This led the scientists to suspect that some substance in the pancreas somehow prevented diabetes.
• It would take another 30 years for scientists to find this magic pancreatic substance—insulin. This discovery, one of the greatest of modern medical history, is discussed in chapter 13.
Too Much Glucose
People with diabetes don’t produce enough or don’t produce any insulin. Or they don’t use insulin effectively. This results in a buildup of too much glucose in their blood.
In all types of diabetes, glucose does not get into the cells that need it and instead builds up in the bloodstream. In addition, cells don’t have the energy they need to do their work.
The buildup of glucose in blood can have various effects, depending on its severity. For one thing, the body may try to flush out excess glucose by filtering it through the kidneys and expelling it from the body in urine. Therefore, people with high levels of glucose in their blood may urinate a lot or feel thirsty because of dehydration.
In other cases, the body may try to “grab” energy from muscle and stored fat cells because it can’t get energy from glucose in the blood. This can cause muscle deterioration and weight loss.
Symptoms of High Blood Glucose
People with very high blood glucose levels share many similar symptoms. You may have had some of these symptoms before you were diagnosed with diabetes.
Some Early Symptoms of Diabetes
• Extreme thirst
• A frequent need to urinate
• Blurred vision
• A feeling of being tired most of the time for no apparent reason
However, some people do not have any symptoms of high blood glucose. Because the signs of diabetes can be so mild, many people walk around for years with dangerously high glucose levels, which can lead to long-term damage. In fact, many people don’t realize they have diabetes until they begin to suffer from complications of the disease.
Of course, only a health care provider can make an accurate diagnosis of diabetes. A trip to the doctor is the next logical step if you or someone you love has symptoms of diabetes or you run a risk of developing diabetes.
Glucose Tests
Although you or your health care provider may suspect that you have diabetes because of your symptoms, the only sure way to tell is with glucose tests.
Diabetes causes your blood glucose levels to be above normal some or all of the time. Your blood glucose levels may be high even though you haven’t eaten recently. So, checking the amount of glucose in your blood can determine whether you have diabetes or not. There are four types of tests used to diagnose diabetes: A1C test, fasting plasma glucose test, random plasma glucose test, and two-hour oral glucose tolerance test.
Plasma glucose tests measure the amount of glucose in the plasma of your blood to determine whether the level is higher than normal. Plasma glucose is different from whole-blood glucose, which contains blood cells. In the laboratory, your blood sample is spun in a machine to remove blood cells, platelets, and cell debris. Only the plasma is left. Scientists measure the amount of glucose in the plasma, and these numbers can be 15% higher than whole-blood readings.
A1C Test
• The A1C test can be used to diagnose diabetes.
• Blood is collected from a fingerstick or vein.
• A1C values represent average blood glucose levels over the past 2–3 months.
• The test measures the concentration of hemoglobin molecules that have glucose attached to them. The measure is given as a percentage. An 8% level means that 8% of your molecules are glycated (sugar coated).
• An A1C of 6.5% or higher is used to diagnose diabetes.
Fasting Plasma Glucose Test
• In diabetes, extra glucose remains in the blood, even after fasting.
• For this test, you will be asked not to eat or drink anything but water for at least 8–10 hours. Then, a sample of your blood is taken and the amount of glucose in the blood is measured.
• For those without diabetes, the amount of glucose after fasting is usually less than 100 mg/dl.
• However, when the amount of fasting plasma glucose is 126 mg/dl or higher, diabetes is suspected. A firm diagnosis of diabetes is made when two fasting plasma glucose tests, done on different days, are at least 126 mg/dl.
Random Plasma Glucose Test
• The simplest way to detect diabetes.
• This test measures the amount of plasma glucose at any given time and is done without fasting.
• You may be diagnosed with diabetes if your plasma glucose is 200 mg/dl or higher and you have obvious symptoms, such as frequent urination, intense thirst, blurred vision, unexplained weight loss, and extreme tiredness.
Oral Glucose Tolerance Test
• This test can also be used to diagnose diabetes.
• For this test, you will be asked not to eat or drink anything overnight. Then, in the morning, a sample of your blood is taken before and two hours after you have a drink that contains glucose.
• If your fasting plasma glucose is 126 mg/dl or higher and/or your post-drink plasma glucose is 200 mg/dl or higher, then you will be diagnosed with diabetes regardless of your symptoms.
Categories of Increased Risk for Diabetes
Sometimes increased risk for diabetes is apparent before diabetes develops. If your fasting plasma glucose test is greater than 100 mg/dl but less than 126 mg/dl, you
