Blood Sugar Testing

What Is Diabetes? Why Do I Need a Blood Sugar Test?

Diabetes is a group of metabolic disorders marked by elevated blood-sugar levels that extend for long periods of time. It usually results from insufficient quantities of insulin or from insulin’s resistance to properly regulating blood-sugar levels. Diabetes is typically a chronic condition, meaning that it can be controlled but not cured by medical intervention and personal behaviors. There are type 1, type 2, and gestational forms of this disease.

Blood-sugar testing plays a critical role in both diagnosing and managing diabetes. It is particularly important in gauging the effectiveness of diet, exercise, and medications in regulating glucose levels in the bloodstream. At Baptist Health, we care for persons with diabetes every day, helping them manage their condition, and enabling them to lead the lives they want to lead.

What Does a Blood Sugar Test Do?

A blood-sugar test is a procedure for measuring glucose levels in the blood. Derived from carbohydrates in food, glucose is the human’s body main source of energy. Testing for glucose levels in the blood has two primary purposes:

  • The diagnosis of diabetes or prediabetes by a physician
  • The management of diabetes by someone who has been diagnosed with this condition.

There are two major types of blood-sugar tests for diagnosing diabetes:

  • Fasting blood sugar (FBS) test: An FBS test measures blood glucose levels at the time that it’s taken. You are required to fast – neither eat nor drink – for at least eight hours beforehand. (A similar test without fasting is called a random plasma glucose, or RPG, test.)
  • Hemoglobin A1C test: A hemoglobin A1C test estimates an average for glucose levels over the most recent three-month period. The results will be stated as a percentage. Normal blood-sugar readings are below 5.7 percent; prediabetes is a range between 5.7 and 6.4 percent; and diabetes is greater than or equal to 6.5 percent.

Separate tests are used to diagnose gestational diabetes. Included are the glucose challenge test and the glucose tolerance test.

When Should I Test My Blood Sugar?

Blood-sugar testing for diagnostic purposes will occur during doctor’s office visits. If, however, you are diagnosed with diabetes, you will need to monitor your blood sugar levels on a daily basis. Reasons for doing so include:

  • Determining the effectiveness of your medications, including insulin, in controlling your blood glucose
  • Seeing whether lifestyle changes, including diet and exercise, are having a positive impact on your condition
  • Avoiding high-risk situations, when your blood sugar levels are dangerously high or low
  • Measuring your progress against the treatment goals established by you and your physician.

Testing Times for Type 1 Diabetes

People with type 1 diabetes generally test their blood-sugar levels between four and ten times daily, including:

  • Before all meals
  • Before snacks
  • Before or during exercise or periods of physical exertion
  • Before going to bed
  • Sometimes at night.

You may need to test more often when you’re ill, starting a new medication, or undergoing a major change in routine.

Testing Times for Type 2 Diabetes

People with type 2 diabetes taking supplementary insulin often test several times day, including:

  • Before all meals
  • Before going to bed.

You may be able to test less frequently if you are only taking intermediate- or long-acting forms of insulin. Individuals managing their diabetes with oral medications and lifestyle changes rather than insulin are not required to test daily.

How Do I Test My Blood Sugar?

There are two methods for conducting blood-sugar tests at home. Both require the use of a blood-sugar meter:

  • Finger-stick method: With this method, you use a small needle called a lancet to draw a drop of blood from the finger. This blood is absorbed by a test strip, which is fed into the blood-sugar meter. The meter provides a blood-glucose reading within a minute or two.
  • Continuous glucose monitor (CGM): A second method involves the use of a continuous glucose monitor or CGM. A CGM is a small computerized device that provides regular blood sugar readings by means of a sensor inserted underneath the skin. CGMs are often used in conjunction with insulin pumps. The period of their effectiveness ranges from two weeks to three months, at which point they need to be replaced.

The finger-stick method is the more fundamental of the two testing types, because CGMs must be recalibrated on a daily basis with a finger stick. Testing by finger stick involves the following steps:

  • Cleaning the hands with soap and water
  • Placing a test strip in the blood-sugar meter
  • Pricking the side of a finger with a lancet to produce a blood drop
  • Dipping the end of the test strip into the blood drop until the latter is fully absorbed
  • Noting the blood-glucose reading on the meter once it appears.

Be sure to alternate fingers when conducting finger-stick testing.

Interpreting Blood Glucose Levels

Blood-glucose readings will generally fall into the following ranges:


People without Diabetes

People with Diabetes

Before breakfast

Under 70-99 mg/dL

Between 80-130 mg/dL

Before lunch, dinner, and snacks

Under 70-99 mg/dL

Between 80-130 mg/dL

Two hours after eating

Under 140 mg/dL

Under 80-130 mg/dL

mg/dL = milligrams per deciliter


You can use these guidelines as targets for your diabetes treatment plan. If you have trouble hitting the ranges, speak with your physician about adjusting your medications or making other changes in how you manage your condition. Keep in mind that target ranges should reflect personal characteristics, such as age, overall health, pregnancy status, and other pertinent factors.

Learn More About Blood Sugar Testing at Baptist Health

If you have questions about blood-sugar testing for diabetes, or want to schedule an appointment with one of our specialists, contact your Baptist Health primary care physician.