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Glucose Monitoring Devices

What is blood sugar (glucose) monitoring?

Blood sugar levels give you information about how well your diabetes is under control. They also tell you how well your plan of diet, exercise, and medicine is working. Keeping your blood sugar levels near normal may reduce or prevent your risk for problems (complications).

Man looking at glucose meter.

How can blood sugar levels be checked?

Checking blood sugar levels regularly is very important in good diabetes management. Most methods of blood sugar monitoring need a blood sample. Blood sugar monitoring can be done at home with a variety of devices. They take the blood sample by pricking your skin with a small tool. A small device called a glucose meter or glucometer measures how much sugar is in the blood sample.

The drop of blood you get with a finger prick is often enough to use on a test strip. A finger prick can be done with a special needle (lancet) or with a spring-loaded device that quickly pricks the fingertip. You place the drop of blood on the test strip. Depending on the type of meter used, you may put the strip into the meter before or after you put the drop of blood on the test strip. The meter then reads the blood sugar level. Most meters are made to be used with the finger prick blood drop. But some meters can also be used with blood taken from the forearm or other site.

You can choose from many types of monitors. They range in price, ease of use, size, portability, and length of testing time. Each monitor needs a specific test strip. Generic strips or strips for other monitors may give inaccurate readings. Always refer to your user's manual for directions. Most blood sugar monitors give accurate results if used correctly. Most give results within seconds. Some monitors can also talk. They give directions and results that you can hear. This is helpful if you have vision problems. Or if you have physical problems that make it hard for you to see the results. Some monitors can give spoken directions in Spanish and other languages.

Some monitoring devices can monitor blood sugar continuously for several days at a time. You may be able to set an alarm on the device. This can warn you if you blood sugar gets too low or too high. 

You may have to check your blood sugar levels 4 or more times a day. Blood sugar levels can be affected by several things. These include:

  • Diet

  • Diabetes medicine

  • Exercise

  • Stress

  • Illness

Some blood sugar monitors can store your results. You may be able to send this information to your healthcare provider's office electronically. You can also send this information to your home computer or mobile device. One advantage of this type of monitor is that it can show you your blood sugar levels as a graph. Mobile blood sugar monitoring apps are also available for tracking and sharing blood sugar results.

What are noninvasive blood sugar monitors?

A finger prick can become painful and difficult if you need to do this on a regular basis. Several devices that don't need a blood sample are being developed. But most of these have not been approved by the FDA. Some of these devices use one of the following ways to measure blood sugar:

  • Infrared light to shine through a forearm or finger

  • Low-level electricity to draw blood up through the skin

  • Saliva or tears

To find out if a monitor is approved for use, check the FDA website's section on blood glucose monitoring devices .

Continuous glucose monitoring (CGM)

If you have type 1 or type 2 diabetes and want to manage your blood sugar better, CGM may be right for you. It tracks your blood sugar level during the day and night. This can help you make better choices about food, physical activities, and taking medicines. It can also find trends and patterns that can help your healthcare provider better manage your diabetes. Besides giving you your blood sugar at any moment, CGM also gives you the percentage of time your blood sugar has been in the normal range (or too high or too low.) This percentage is called time in range (TIM). For most people the target is 70% and the target range is between 70 and 180 mg/dL. These target numbers are adjustable according to your age and other conditions.

CGM is a safe, effective treatment for people with type 1 diabetes and for certain people with type 2 diabetes. CGM devices should be considered soon after diagnosis of diabetes that requires insulin management. They are ideal for people who need to have tight blood sugar control to keep blood sugar from getting too high or too low. Thy are also helpful for people who may not recognize symptoms of low blood sugar. Ask your healthcare provider if CGM is right for you.

Several CGM devices are available. They are approved by the FDA with a prescription from a healthcare provider. The devices have a sensor, transmitter, and a receiver or monitor. The sensor is a small device placed under the skin. It will measure your blood sugar several times a minute. A transmitter sends the information to a receiver. This may be a part of an insulin pump or a separate device.

Your blood sugar may still need to be checked a few times a day with a regular glucose meter to check for accuracy. With most CGM models, the sensor under the skin needs to be replaced every 7 to 14 days. At least 1 model uses a sensor that is implanted under the skin and can function for up to 180 days. Implanted sensors must be placed and removed by your healthcare provider.

What are healthy blood sugar level ranges?

Blood sugar levels over 180 mg/dL (mg/dL = milligrams of glucose per deciliter of blood) or under 70 mg/dL are considered unhealthy. High blood sugar levels (above 180 mg/dL) may be a sign of not enough insulin, caused by overeating, lack of exercise, or other factors. Low blood sugar levels (below 70 mg/dL) may be caused by taking too much insulin or other diabetes medicines, skipping or delaying a meal, over exercising, drinking too much alcohol, or other factors.

> 180 mg/dL

Too high; considered unhealthy

80 - 130 mg/dL

Good range for most people

< 70 mg/dL

Too low; considered unhealthy

The American Diabetes Association (ADA) advises a before-meal (preprandial) plasma glucose level of 80mg/dL to130 mg/dL. The ADA has set the after-meal (postprandial) plasma glucose level of less than 180 mg/dL.

These are the most common symptoms of high blood sugar (hyperglycemia). But each person's symptoms may be different. And in some cases there may be no symptoms at all. Symptoms may include:

  • Quick, unexplained weight loss

  • Feeling sick

  • Intense thirst

  • Increased urination

  • Vomiting

  • Severe tiredness (fatigue)

  • Blurred vision

  • Fainting

These are the most common symptoms of low blood sugar (hypoglycemia). But each person's symptoms may be different. Symptoms may include:

  • Hunger

  • Fatigue

  • Shakiness

  • Headaches

  • Confusion

  • Dizziness

  • Sudden moodiness or behavior changes

  • Sweating

  • Fast heartbeat

  • Pale skin color

Sometimes none of these warning symptoms appear before a person loses consciousness from low blood glucose. The loss of the ability to sense low blood sugar is called hypoglycemia unawareness. 

Insurance and blood glucose monitoring

Check with your insurance company to find out if blood glucose monitoring equipment and testing supplies are covered under your plan. If not, many suppliers offer rebates or discounted prices on trade-ins.

In addition, when selecting a glucose meter, the ADA reminds consumers to factor in the ongoing cost of test strips. Test strips can cost between 50 cents and $1 per strip. Insurance providers vary on how many strips and how much of the test strip cost they will cover. 

Medical Reviewers:

  • Marianne Fraser MSN RN
  • Raymond Kent Turley BSN MSN RN
  • Robert Hurd MD