Self-Monitoring of Blood Glucose

Reviewed by: HU Medical Review Board | Last reviewed: February 2021.

Monitoring your blood glucose is an important part of managing type 2 diabetes. Knowing your numbers helps you understand whether your diabetes treatment plan is working. It also guides you to make changes to fine-tune your blood glucose level.

Your doctor will monitor trends in your blood glucose using the A1C test during office visits. You may also need to track your blood glucose levels at home, especially if you:1

  • Take insulin
  • Are pregnant
  • Are having a hard time controlling your blood glucose levels

Your doctor will tell you how often you need to test yourself between office visits.1

You will use a blood glucose meter (glucometer) to check your blood glucose level at home. Some people also need a continuous glucose monitor (CGMs).1

How to use a blood glucose meter (glucometer)

There are several steps to follow when you test your blood glucose at home. You will be breaking the skin to take a drop of blood. This means you need to keep your hands and tools as clean as possible to prevent infections. Steps for using a glucometer include:1,2

  • Wash and dry your hands
  • Insert a test strip into your meter
  • Use your lancet (sharp) to draw a drop of blood from your finger
  • Touch the drop of blood to the test strip
  • Place the test strip in the monitor
  • Your blood glucose number will appear on the screen in seconds
  • Write down your results with the day and time, or record them in an app
  • Write down anything that may have affected your results, such as food, exercise, dehydration, or stress

This is generally how blood glucose self-monitoring works. There are many types of blood glucose meters, and some may work slightly differently. Always read the instructions before using a new meter.

What your blood glucose numbers mean

Your doctor will give you a target range of what your blood glucose levels should be before eating and 1 to 2 hours after eating. The number may look something like this: 80 to 130 mg/dl. Your blood glucose target will depend on several things, such as:1

  • How long you have had diabetes
  • Your age and overall fitness
  • Your A1C test results
  • Other health conditions you may have

Pay attention to whether your numbers are higher or lower than the range your doctor gave you. If your numbers are too high or too low for several days (when taken at the same time of day), talk to your doctor. You might need to change your diabetes care plan.

To correctly interpret your results, you and your doctor will need to know about several things that can impact blood glucose levels. This is why, in addition to your blood glucose numbers, you should also note:1,2

  • Time of day
  • Activity and exercise
  • Food and drink
  • Diabetes drugs taken, including time and dose
  • Any stress or illness you are having

Blood glucose numbers that are too high or too low can mean many things. By tracking your numbers, you will learn how many and what types of carbohydrates affect your numbers the most. Or, you may learn that you need to drink more water, change your mealtimes, or change how much you exercise.2

Tips for blood glucose home monitoring

How often you will need to test your blood glucose outside of doctor’s visits is different from person to person. Your doctor will tell you how often to take a reading. Here are some tips for monitoring your blood glucose levels:1-4

  • Never share your fingerstick lancet or blood glucose meter. You do not want to risk sharing an infection or blood-borne infection like hepatitis or HIV.
  • Do not use alcohol to clean your hands. It dries the skin too much. Warm water and soap are best.
  • Avoid using a lancet more than once, if you can. A dull lancet causes more pain and injures the skin.
  • Spring-loaded lancets make sticking yourself less painful.
  • Stick yourself on the side of your finger near the nail to avoid creating a sore spot where you use your finger the most.
  • You can draw blood from your forearm, thigh, or fleshy part of your hand with some meters. This prevents any one spot from becoming sore or infected.
  • Keep your test strip container closed and away from moisture, extreme heat, or extreme cold.
  • If you have trouble getting enough blood, try shaking your hand, placing your finger in warm water, or squeezing (milking) your fingertip before sticking yourself.
  • Always put used lancets in a sharps container. Never toss sharps in the trash.

How accurate are home blood glucose monitors?

Glucometers are generally accurate, but different machines may give slightly different results. Also, the accuracy can be affected by the test strip and how well the device is working.

Other things that affect the accuracy of home blood glucose monitors include:3

  • How closely you follow the instructions for your device
  • Whether test strips are properly stored
  • Whether you are anemic or dehydrated
  • Temperature, humidity, and altitude

Your device may also come with a control solution that you use in place of blood to test the machine’s accuracy. It is a good idea to regularly bring your blood glucose meter to your doctor appointments and compare its results to your lab results.3

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