How to Test Blood Sugar

Monitoring blood sugar levels is an essential part of successfully managing diabetes.

When you have an idea of what your blood sugar is, you’ll be better equipped with the knowledge to make a plan of action.

Without checking your blood sugar independently, the only other time you’d have some insight as to how your blood sugars are running is at your visits with your healthcare provider. This may occur only every 3-6 months.

By testing your blood sugar, you’ll be more in the driver’s seat of your long-term health.

Diabetes and Blood Sugar

Diabetes mellitus, or diabetes, is a disease when blood sugar (blood glucose) levels are considered too high. Diabetes can be classified as either type 1 or type 2, with the more prevalent type being type 2.

Type 1 diabetes occurs when the pancreas can no longer make sufficient amounts of insulin, which is a hormone responsible for keeping blood sugar levels at a healthy level.

Type 1 diabetes is an autoimmune disease where the body attacks its own cells; in this case, the beta cells in the pancreas that make insulin.

Type 2 diabetes tends to occur more from insulin resistance.

This is when the body doesn’t use insulin the way it should, resulting in high blood sugar levels. People with type 2 diabetes don’t necessarily need to take insulin to survive, as is the case with type 1 diabetes.

However, some people with type 2 diabetes can have some amount of pancreatic insufficiency, which is managed similarly to type 1 diabetes.

Blood sugars rise when we eat, especially carbohydrate foods, which turn into sugar to give our cells energy. Blood sugar levels are also impacted by illness, physical activity, stress, and even certain medications.

Blood sugar is typically measured in milligrams per deciliter, or mg/dL.

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Why you should test blood sugar

Without knowing what your blood sugar numbers are, you’re essentially in the dark until the time of your next blood test with your healthcare provider.

This is usually only a few times per year. Here are several reasons for regular at-home blood glucose testing:

  • Monitor the effectiveness of diabetes medications. Whether you’re newly diagnosed or have had diabetes for years, it’s important to be aware of how effective your medications are. Sometimes medication can start to lose its effectiveness over time, possibly warranting the addition of another medication or dose change.

  • Insulin dosing is highly dependent on blood sugar levels. Therefore, checking blood sugar several times a day at specific times can help your healthcare provider or diabetes educator make adjustments to your dosage. This can help to keep your blood sugar at the target while reducing the risk of low blood sugar, or hypoglycemia.

  • Learn how different foods affect blood sugar. Many people with diabetes try to be mindful of their eating habits to promote healthy blood sugar levels. By keeping a food journal and recording blood sugar levels, you can start to see patterns that can help you make adjustments to your eating choices.

  • Assess how lifestyle changes are impacting blood sugar. Physical activity can lower blood sugar, so checking blood sugar can be a positive reinforcement for those taking steps to improve long-term health with diabetes.

  • Help prevent low blood sugar. Checking blood sugar levels and seeing a lower-than-normal result can help you avoid a critically low blood sugar. For example, if your blood sugar level is 80 mg/dL at bedtime, you may decide to take a lower dose of nighttime insulin or eat a snack before bed to prevent it from going lower.

  • Identify life-threatening health conditions. Very high blood sugar can be a result of diabetic ketoacidosis (DKA), which happens in people with type 1 diabetes and can be life-threatening. In people with type 2, uncontrolled high blood sugar could be due to hyperglycemic hyperosmolar syndrome (HHS). Both of these conditions warrant a visit with a healthcare provider, so checking blood sugar can help you identify when it’s time to get medical help.

  • Monitor gestational diabetes (GDM). Some pregnant women develop diabetes during pregnancy without having had a diagnosis of diabetes previously. Blood sugar levels can often return to normal after pregnancy. However, it’s crucial for the health and development of their baby that blood sugar levels stay within normal levels. Many women with GDM monitor their blood sugar up to four or five times per day.

  • Assess long-term diabetes control. Your healthcare provider will likely check your hemoglobin A1c level once every 3-6 months to assess your overall blood sugar control.

    The hemoglobin A1c gives an average blood sugar measured over the past 90 days, so it’s a great “big picture” test. Hemoglobin A1c results are reported in a percentage, which equals the percentage of red blood cells that had a glucose (sugar) molecule attached to it.

When is the best time to test blood sugar?

At a very minimum, people with diabetes should check their fasting blood sugar. Fasting blood sugar refers to the blood sugar level after waking but before eating.

Because it’s tested without having eaten for at least eight hours, fasting blood sugar gives a good idea of your baseline blood sugar before other factors are added in, such as diet and activity levels.

Checking before and after meals is very helpful in assessing how much diet changes blood sugar. If blood sugar were 130 mg/dL before lunch and 200 mg/dL two hours after lunch, it would be a good idea to evaluate what the meal was, adjust the mealtime insulin dose, etc.

Pre-meal blood sugar is often referred to as preprandial blood sugar and after-meal blood sugar as postprandial blood sugar.

Finally, checking blood sugar at bedtime helps provide information about how blood sugar might change while sleeping. Some people with diabetes experience something called the dawn phenomenon, which results in high fasting blood sugar, even if blood sugars were normal at bedtime.

Adjusting nighttime insulin doses can help with the dawn phenomenon. Bedtime blood sugar is sometimes shortened to HS, which is an abbreviation of the Latin term for “at bedtime.”

How to test blood sugar

You’ll need a glucometer kit to test your blood sugar. A glucometer is also referred to as a blood sugar meter, and it analyzes the sugar content of your blood based on a small blood sample.

You’ll also need lancets, which are small needles used to prick the skin in order to obtain a small blood sample, and a lancing device to use each lancet.

Test strips are used to absorb the blood sample and are inserted into the glucometer in order to obtain the reading.

Glucometer kits are available over the counter without a prescription. However, obtaining a prescription and getting your glucometer supplies through insurance is often much more affordable.

Most insurance companies cover enough supplies (lancets and test strips) for people with diabetes to check their blood sugar depending on whether or not insulin is taken.

Some glucometers require coding before use. Therefore, it’s essential to check the manual for your individual meter prior to use for instructions on how to perform the coding.

Step By Step Guide

Once you have a glucometer, here are the steps to checking your blood sugar:

Step 1: Wash your hands with soap and water and dry thoroughly. Monitoring blood sugar using dirty hands may alter the accuracy of the reading.

Step 2: Load one lancet into the lancing device. Only one lancet should be used for each blood sugar test. Reusing lancets multiple times can dull the end of the needle and make finger sticks more painful.

Step 3: Insert a test strip into the glucometer; this often turns the glucometer on, but if not, turn the machine on prior to inserting the strip.

Step 4: Use the lancing device to prick the side of one of your fingers. Avoid using the direct pad of your finger as this can cause pain when doing things like typing later on. (Fingersticks are the most accurate testing site, but alternative testing sites can be used.)

Step 5: Gently apply pressure to the lanced finger (don’t squeeze too hard or “milk” the finger) until a small bead of blood appears. Apply the bead of blood to the end of the test strip, which should absorb the sample immediately.

Step 6: Wait while the glucometer obtains a reading, which usually takes around 10-15 seconds. If an error message occurs, consult the user manual for the glucometer.

Step 7: Record the reading in a blood glucose log (many glucometers store results, so this is an option.) Dispose of the used lancet in a biohazard sharps container, not the garbage (used strips can go in the garbage.)

What is normal blood sugar?

According to the American Diabetes Association (ADA), these are the goals for blood sugar in those with diabetes, though individual blood sugar goals may vary.

The American Association of Clinical Endocrinologists (AADE) has more strict blood sugar goals as follows:

Blood sugar goals for women with gestational diabetes are the most strict, as high blood sugar during pregnancy can lead to adverse outcomes in the mother and baby.

Maintaining blood sugar meters

Glucometers usually last several years with minimal maintenance. Taking care of your glucometer supplies will prolong their usefulness.

According to Accu-Chek, a popular glucometer manufacturer, the battery in your glucometer should last for about 1000 tests. This, of course, varies between glucometer brands.

If your meter starts to show erratic results, you may want to calibrate it. Some glucometers come with a control solution, which is placed on a test strip like a blood sample.

The result that comes up on your meter should fall within a specific range for your meter. If the result is outside of the range, you may need to replace your meter or contact the manufacturer.

Store your glucometer and supplies out of extreme temperatures, as well as extreme humidity.

Tips to control blood sugar levels

If blood sugar levels are falling outside of your desired range, here are some tips to help stabilize them:

  • Take your diabetes medication consistently.

  • Be mindful of your diet; keeping a food journal can help identify potential trigger foods responsible for high blood sugars.

  • When taking insulin, be sure to eat some carbohydrates consistently throughout the day to prevent hypoglycemia.

  • If you’re sick, continue to take your diabetes medication unless instructed otherwise by your healthcare team. If you’re sick and blood sugar levels rise above 300 mg/dL, seek medical advice promptly.

  • Aim to be physically active for an average of 150 minutes per week.


Monitoring blood sugar levels helps people with diabetes managing their condition. Insurance companies often cover the cost of the supplies needed to check blood sugar because it’s helpful for diabetes management.

Being aware of your blood sugar at various times during the day can provide useful information that can lead to adjustments in diet, medication dosing, etc.

Without checking blood sugar outside of routine blood tests, it’s impossible to know how well your diabetes is being controlled, leading to a potentially unpleasant surprise at your next routine blood test.

Take the power into your own hands by routinely monitoring your blood glucose and be an active part of your diabetes self-management plan.

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  4. Rathod SDCrampin ACMusicha C, et al
    Glycated haemoglobin A1c (HbA1c) for detection of diabetes mellitus and impaired fasting glucose in Malawi: a diagnostic accuracy study
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