Monitoring Blood Sugar and Ketones
Accurate monitoring of blood sugar (glucose) is the foundation of good diabetes control. You and your doctor will make decisions about medicine, food and exercise based on your blood glucose numbers. You need to know how to monitor blood glucose levels, record the results, understand the numbers and recognize the patterns.
Blood sugar (glucose) is checked using a device called a blood-glucose meter or glucometer. A small drop of blood (usually from a pricked finger) is placed in the glucometer. The device shows the blood sugar level. It is measured in milligrams per deciliter of blood (mg/dl).
Each check gives one reading of blood sugar. Diabetes experts usually recommend that people with type 1 diabetes check their blood sugar at least three times a day. For tight control of glucose, you may need four daily checks. This means one check before each meal and one at bedtime. Occasionally, it may be sensible to check even more often. You may need to do this if symptoms occur between checks, or if you are adjusting your insulin doses.
An insulin pump that has a built-in sensor is being tested for use in type 1 diabetes. This device has been nicknamed the "bionic pancreas." With this device, it may eventually be possible for some diabetics to stop doing regular finger-stick checks to measure glucose.
Blood glucose readings show how well blood sugar is controlled in response to diet, exercise and insulin. Glucose readings should be recorded in a log (diary or notebook). You should review them regularly with a health care professional.
Blood glucose can be reported in two ways. Sometimes it is reported as the amount of glucose in a sample of whole blood. In this case, the red blood cells take up space and slightly dilute the sample. You also can get a reading of the amount of glucose in a sample of plasma. (Plasma is whole blood with all of the cells removed.)
In the past, most glucometer machines reported glucose levels in whole blood concentrations. Today, most glucometers report plasma concentrations. Find out which number your glucose monitor provides to you. Plasma levels are 10% to 15% higher than whole blood levels. Most glucose "goals" that are set by experts refer to plasma concentrations.
Several national organizations have set goals for "tight" blood-sugar control. This is sometimes called optimum control. The most widely used goals are set by the American Diabetes Association. Tight control means that plasma glucose is 90 to 130 mg/dl before meals. It should be reliably below 180 mg/dl during the two hours after a meal. These targets are based on research. The studies showed that keeping blood sugar near normal can reduce the risk of long-term health problems from diabetes.
You and your doctor should set individual goals for you. Tight control is not the right plan for some people. For example, children may be too young to recognize symptoms of hypoglycemia (very low blood sugar). Higher goals may be safer for them. Older adults with heart disease also might need higher goals. For them, low blood sugar might cause more dangerous symptoms. Some people don't have symptoms to alert them when blood sugar gets low. For this reason, they also may choose higher blood sugar goals.
Daily monitoring helps to keep track of the short-term highs and lows in your blood sugar. The hemoglobin A1C test gives a longer-term view. This blood test shows how well diabetes has been controlled during the last two to three months. The test also is called HgbA1c or simply A1C.
The A1C test normally is done in a lab or doctor's office. It measures how much glucose is attached to hemoglobin, the iron-carrying protein in red blood cells. Hemoglobin with glucose attached is called "glycated" or "glycosylated" hemoglobin. When you have more sugar in the blood, you form more glycated hemoglobin in the red blood cells.
Once glucose is attached, it does not come off. Red blood cells survive only two to three months. This means the effect of high sugar levels will disappear gradually as red blood cells are broken down and recycled. The A1C reports what percentage of your red cells are "glycated." This gives an idea of how much sugar has been in the blood during the time the current blood cells have been circulating. It reflects your sugar average for the last two to three months. However, the test is affected most heavily by the most recent two weeks before your test.
Adults can reduce the risk of complications from type 1 diabetes by keeping their A1C level lower than 7%. For people under age 19 who have type 1 diabetes, slightly higher A1C targets are usually preferred. Discuss your age-specific A1C goal with your doctor.
You should have your A1C tested at least every six months. More frequent testing is a good idea if your sugar is not in good control.
The U.S. Food and Drug Administration recently approved the sale of a home monitor for A1C. Home monitoring, however, should not replace regular visits to your doctor.
A person with diabetes sometimes needs to test to see if ketones are in the urine. If your body does not get enough insulin, it can't use glucose for energy. When this happens, your liver is programmed to make emergency fuels. These fuels are made from fat and are called ketones.
Small amounts of ketones in the urine may mean that this process is starting. Although they supply energy, ketones are toxic at high levels. Moderate or high ketone levels can be a sign of a dangerous condition called ketoacidosis. This condition can result in coma or even death.
You generally will notice symptoms if ketone levels are getting high. The symptoms are a warning that you should check your urine for ketones. Symptoms include:
- Blood sugar levels over 240 mg/dl
- A cold or other illness
- Extremely tiredness
- Nausea or vomiting
- Abdominal pain
- Difficulty breathing
- "Fruity" odor on the breath
Ketone levels can be tested using a special strip that is dipped into the urine. The strip will change color. This color is compared to a chart on the strip container that shows the amount of ketones in the urine.
If your results show that the number of ketones is "moderate" or "large," contact your doctor immediately. Don't exercise when you have detected ketones in the urine, even if your symptoms are only mild. It is likely that you are dehydrated. Also, physical activity at this time can cause the body to burn fat. This could cause you to create a larger amount of dangerous ketones.
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