Blood Sugar Testing

Glucose is a type of sugar that is found in your blood. Blood sugar (glucose) testing is a big part of caring for your diabetes. A blood sugar test tells you how much sugar is in your blood at any point in time. Many things affect your blood sugar levels each day. Testing will let you know if your meal plan, medication and exercise are working to keep your blood sugar in good control.

Who should test their own blood sugar?

Anyone with diabetes should test their blood sugar because  diabetes changes the way your body controls blood sugar levels. Self-testing helps you keep your blood sugar levels as close to normal as you can.

How can blood sugar self-testing help me?

You and your healthcare team have set up a plan to help you control your blood sugar. One of the best ways to be sure your plan is working is to test your blood sugar yourself. Research shows that good control of blood sugar can lower your risk of eye disease, kidney disease and nerve damage that can develop due to diabetes. Self-testing lets you learn how diabetes makes your body react to daily events. You can answer questions like, "What happens to my blood sugar during times of stress or when I am sick?" or "What happens to my blood sugar when I exercise?" Self-testing can help you decide how to take better care of yourself.

How often should I test my blood sugar?

The more you test, the more you will know about your blood sugar control. Many things affect your blood sugar each day, like eating, exercise, medication, illness and stress. So, it is important to test your blood sugar at different times of the day. Research studies show that testing your blood sugar daily, up to 4 times or more, is a good way to learn how to better control your blood sugar. Good control of blood sugar will help you lower your risk of future problems with diabetes. Self-testing gives you the information you need to avoid too many high or low blood sugar levels day-to-day. Your healthcare team will help you decide how often to test. 

When should I test my blood sugar?

Your healthcare team will also help you decide when to test. Testing at different times is a good idea. Here are some useful times to choose from:

  • Before breakfast. This is called the fasting blood sugar. Fasting means you have not had any food in 8 hours or more. 
  • 1-2 hours after breakfast. This is called the postprandial blood sugar. 
  • Before lunch. 
  • 1-2 hours after lunch. 
  • Before supper. 
  • 1-2 hours after supper. 
  • Before bedtime. 
  • At 2:00 or 3:00 a.m., if you take insulin.

It is a good idea to do extra tests when:

  • There are changes in your treatment plan.
  • You start a new medication for diabetes. 
  • You think your blood sugar might be too low or high. 
  • You are sick. 

How do I make sense of different blood sugar levels at different times?

Blood sugar levels 1 to 2 hours after eating are called postprandial. Research shows that blood sugar levels in people with diabetes can more than double after eating, even when their blood sugar before eating is normal. It is helpful to talk about your fasting and postprandial sugar goals with your healthcare team.

Do I really need to keep records?

Yes, keep a written record (logbook) of your blood sugar readings. Also, write down the date, time and whether the self-test was done before or after eating. 

What can I do to improve my self-testing?

Follow the directions that come with the meter you are using. Talk to your healthcare team about your meter and the way to self-test. These tips will help you get the most correct results.

  • Keep your meter clean. 
  • Keep your testing supplies at room temperature. 
  • Check the expiration date of your testing supplies. 
  • Wash your hands in warm, soapy water. 
  • Dry them well. 
  • Put your hand down to let gravity help the blood flow to your fingertips. 
  • Prick the side of your finger with a fresh lancet in a lancing device. 
  • Get enough of a blood drop to apply to the test strip or test sensor. 
  • Record your results.

What do I do if my blood sugar levels are high?

  • Find out the reason for your high blood sugar level, or call your doctor or diabetes educator. 
  • Drink more water and sugar-free fluids. (Limit fluids with sugar, including fruit juices.) 
  • Follow your recommended meal plan. (If you do not have a plan, meet with your dietitian.) 
  • Take your medication as prescribed by your doctor. If your blood sugar remains high, see your doctor or diabetes educator. 
  • Test your blood sugar more often (every 3 to 4 hours). 
  • If your blood sugar level is below 285 mg/dL and you feel well, increase your physical activity (for example, go for a walk). Always ask your doctor before starting a new exercise routine. 

What do I do if my blood sugar levels are low?

  • Eat or drink fast-acting sugar such as:
    - 3 sugar or dextrose tablets
    - 4 hard candies
    - 1/2 cup of juice or regular soft drink
  • Wait 10 to 15 minutes, then check your blood sugar again. If your blood sugar is still below 75 mg/dL, repeat treatment and blood sugar test again.

The more you test, the more you will know about your blood sugar management. Ask your doctor or diabetes educator what your levels should be.

For more information about testing, please see About Testing in the About Diabetes section.