Guidelines for Blood Glucose Monitoring

When to Test If You Have Type 1, Type 2 or Gestational Diabetes

Blood glucose testing is a way of monitoring the levels of glucose (sugar) in the blood. It's a key aspect of managing diabetes: Done regularly, it can indicate how well insulin supplements, medication, lifestyle changes, and other aspects of diabetes care are working to keep your glucose levels from spiking too high (hyperglycemia) or dipping too low (hypoglycemia).

Either situation can cause damage to your body over many years, leading to potentially serious complications. Research has shown that regular glucose testing reduces the risk of that happening, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDKD).

To do this, you'll use a device called a blood glucose meter that can measure the level of sugar in your blood, usually based on a single drop from your finger (although some monitors can be used on the forearm, thigh, or fleshy part of the hand). Most devices are designed to do single tests, but there are some that provide continuous glucose monitoring.

Who Should Monitor Blood Glucose?

If you've been diagnosed with type 1 or type 2 diabetes, or you're pregnant and have developed gestational diabetes, a form of the disease that occurs during pregnancy and goes away after a baby is born, testing your blood glucose levels regularly and at specific times throughout the day will be a key aspect of managing your disease.

It will be helpful to keep a log of your results, as well as details about what you've eaten throughout the day and how much physical activity you've gotten. With this information, you and your doctor can get a grasp on how certain foods or activities affect your blood sugar and what adjustments you should make to meet your target goals.

Target Blood Glucose Goals
Diabetes Type Fasting Glucose Before Meals 2 Hours After Meals
Type 1 and Type 2 Diabetes N/A 80 to 130 mg/dl Below 180 mg/dl
Gestational Diabetes No higher than 95 mg/dl  No higher than 140 mg/dl No higher than 145 mg/dl
Based on ADA general recommendations; your doctor may determine your goals are different.

Type 1 Diabetes

Type 1 diabetes is an autoimmune disease in which the pancreas does not produce the insulin necessary to keep blood sugar levels steady. People who have this form of diabetes will need to manage it for their entire lives by taking supplemental insulin and by monitoring their blood sugar levels.

According to the Mayo Clinic, this may mean testing four to 10 times a day:

  • Before meals
  • Before snacks
  • Before and after exercise
  • Before bed
  • Sometimes during the night

Situations in which it may be necessary to test more often include:

  • During an illness
  • When there's a change to the daily routine
  • When beginning a new medication

Type 2 Diabetes

In type 2 diabetes, the pancreas does not stop producing insulin altogether; instead, it produces less of it or the body becomes less sensitive to it. Depending on the extent to which this happens, a person with type 2 diabetes may need to take supplemental insulin, in which case blood glucose monitoring typically is recommended.

How often will depend on the type of insulin used. Someone who takes multiple injections throughout the day may need to test his or her blood glucose level before meals and at bedtime, according to the Mayo Clinic. For those who take only long-acting insulin, testing twice a day is often enough.

The NIDDKD also advises doing a blood sugar check any time symptoms of hyperglycemia or hypoglycemia appear.

Gestational Diabetes

Most women who develop diabetes during pregnancy will be advised to test their blood sugar up to five times a day. Here's when:

  • First thing in the morning before eating to determine fasting glucose
  • One to two hours after breakfast
  • One to two after lunch
  • One to two after dinner
  • Just before bedtime

Blood Glucose Testing and Prediabetes

It isn't necessary for most people with prediabetes, also known as impaired glucose tolerance, to monitor their blood glucose levels. What's most important is taking steps to prevent type 2 diabetes by making changes to diet, physical activity level, and other aspects of lifestyle.

It will be at regular yearly checkups that a person with prediabetes will have their blood glucose measured. This is usually done with a blood test called the A1C that can measure average glucose levels over the previous two to three months.

However, if you've been diagnosed with prediabetes, it can't hurt to ask your doctor about monitoring your blood glucose. Doing so will tell you where your blood sugar is every day—information that could help to motivate you to continue to make the changes and take the steps that will help to prevent you from developing type 2 diabetes.

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Article Sources
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  1. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Know Your Blood Sugar Numbers: Use Them to Manage Your Diabetes. Published March 2016.

  2. Centers for Disease Control and Prevention. Diabetes: Monitoring Your Blood Sugar. Updated March 20, 2019.

  3. National Institute of Diabetes and Digestive and Kidney Diseases. Pregnancy if You Have Diabetes. Published January 2017.

  4. Mayo Clinic. Blood Sugar Testing: Why, When, and How. Published May 4, 2018.

  5. National Institute of Diabetes and Digestive and Kidney Diseases. Managing & Treating Gestational Diabetes. Published May 2017.

  6. Middlebeek R and Abrahamson M. Diabetes, Prediabetes, and Glycemic Control in the United States: Challenges and Opportunities. 2014 Apr 15;160(8):572-3. doi:10.7326/M14-0539