Blood sugar testing: Why, when and how

Blood sugar testing is an important part of diabetes care. Find out when to test your blood sugar level, how to use a testing meter, and more.

By Mayo Clinic Staff

If you have diabetes, self-testing your blood sugar (blood glucose) can be an important tool in managing your treatment plan and preventing long-term complications of diabetes. You can test your blood sugar at home with a portable electronic device (glucose meter) that measures sugar level in a small drop of your blood.

Why test your blood sugar

Blood sugar testing — or self-monitoring blood glucose — provides useful information for diabetes management. It can help you:

  • Judge how well you're reaching overall treatment goals
  • Understand how diet and exercise affect blood sugar levels
  • Understand how other factors, such as illness or stress, affect blood sugar levels
  • Monitor the effect of diabetes medications on blood sugar levels
  • Identify blood sugar levels that are high or low

When to test your blood sugar

Your doctor will advise you on how often you should check your blood sugar level. In general, the frequency of testing depends on the type of diabetes you have and your treatment plan.

  • Type 1 diabetes. Your doctor may recommend blood sugar testing four to eight times a day if you have type 1 diabetes. You may need to test before meals and snacks, before and after exercise, before bed, and occasionally during the night. You may also need to check your blood sugar level more often if you are ill, change your daily routine or begin a new medication.
  • Type 2 diabetes. If you take insulin to manage type 2 diabetes, your doctor may recommend blood sugar testing two or more times a day, depending on the type and amount of insulin you need. Testing is usually recommended before meals, and sometimes before bedtime. If you manage type 2 diabetes with noninsulin medications or with diet and exercise alone, you may not need to test your blood sugar daily.

Know your target range

Your doctor will set target blood sugar test results based on several factors, including:

  • Type and severity of diabetes
  • Age
  • How long you've had diabetes
  • Pregnancy status
  • The presence of diabetes complications
  • Overall health and the presence of other medical conditions

For many people who have diabetes, Mayo Clinic generally recommends target blood sugar levels that are:

  • Between 80 and 120 millgrams per deciliter (mg/dL) for people age 59 and younger who have no other underlying medical conditions
  • Between 100 and 140 mg/dL for people age 60 and older, or those who have other medical conditions, such as heart, lung or kidney disease
Dec. 20, 2014 See more In-depth