Blood sugar testing: Why, when and how

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Blood sugar testing: Why, when and how

When you have diabetes, blood sugar testing is the most important thing you can do to feel your best and prevent long-term complications. Consider it an opportunity to take charge of your health.

Know your target range

Your doctor will set your target blood sugar range. For many people who have diabetes, target levels are:

  • Fasting at least eight hours (fasting blood sugar level) — between 90 and 130 milligrams per deciliter (mg/dL) or 5 and 7 millimoles per liter (mmol/L)
  • Before meals — between 70 and 130 mg/dL (4 and 7 mmol/L)
  • One to two hours after meals — lower than 180 mg/dL (10 mmol/L)

Remember that your target blood sugar range may differ, especially if you're pregnant or you develop diabetes complications. Your target blood sugar range may change as you get older, too. Sometimes reaching your target blood sugar range is a challenge. But the closer you get, the better you'll feel.

When to test your blood sugar

How often you test blood sugar levels depends on many factors, including the type of diabetes you have, your individual diabetes treatment plan, and how well your blood sugar is controlled.

  • Type 1 diabetes. Your doctor may recommend blood sugar testing at least three times a day — perhaps before and after certain meals, before and after exercise, and before bed. You may need to check your blood sugar level more often if you're ill or you change your daily routine.
  • Type 2 diabetes. If you take insulin to manage type 2 diabetes, your doctor may recommend blood sugar testing one to three times a day, depending on the number of insulin doses you take. If you manage type 2 diabetes with other medications or with diet and exercise alone, you may be able to test your blood sugar level less often.

How to test your blood sugar

Blood sugar testing requires a blood sugar monitor. Some monitors are large with easy-to-handle test strips, while others are compact and easier to carry. Some monitors track the time and date of each test, the result and trends over time. If you're unsure which blood sugar monitor is best, ask your doctor or diabetes educator for a recommendation.

To test your blood sugar, follow the instructions that come with your glucose meter. In general, here's how the process works:

  1. Before pricking your finger, wash your hands with soap and warm water. Then dry them well.
  2. Remove a test strip from the container and replace the cap immediately to prevent damage to the strips.
  3. Insert the test strip into the meter.
  4. Place the tip of the special needle (lancet) on your finger. Stick the side of your finger, not the tip, so that you won't have sore spots on the part of your finger you use the most.
  5. Hold your hand down to encourage a drop of blood to form. When you have a drop of blood, carefully touch the test strip to the blood (avoid touching your skin with the test strip) and wait for a reading.
  6. Within a few seconds, the meter will display your blood glucose level on a screen.

Your fingertips contain a lot of nerve endings, so make sure to rotate the sites where you stick your fingers. If you have a newer glucose meter, you'll have the option to test your blood glucose from other sites, such as your forearm or thigh. But check with your doctor or diabetes educator first to find out if alternative site testing is appropriate in your case.

Troubleshooting problems

When used correctly, you can count on your blood sugar monitor to provide accurate readings. If you think something's not right, start with the basics:

  • Check the test strips. Throw out damaged or outdated strips.
  • Check the monitor. Make sure the monitor is at room temperature, and the strip guide and the test window are clean. Replace the batteries in the monitor, if needed.
  • Check the code number on the test strips. Some monitors must be coded to each container of test strips. Be sure the code number in the monitor matches the code number on the container of test strips.
  • Check your technique. Wash your hands with soap and water before pricking your finger. Apply a generous drop of blood to the test strip. Don't add more blood to the test strip after the first drop was applied.

If you're still not sure what's wrong, do a quality control test according to the manufacturer's instructions and check the owner's manual for other troubleshooting issues. You can bring the monitor to your next doctor appointment as well.

Recording your results

Each time you perform a blood test, log your results. Record the date, time, test results, medication and dosage, and diet and exercise information in a notebook, record book or journal. Better yet, you may be able to download the information to your computer or transfer the information to a mobile device or an online tracking program. The more complete your records are, the more useful they'll be.

This information helps you see how food, physical activity, medication and other factors affect your blood glucose. As patterns occur, you can begin to understand how your daily activities affect your blood sugar levels. This puts you in a better position to manage your diabetes day by day and even hour by hour.

If your blood sugar readings are consistently higher or lower than your target range — or blood sugar extremes don't respond to adjustments in diet or medication — you may need to revise your treatment plan. In some cases, your doctor may suggest changing your diet or including more physical activity in your daily routine. If that's not effective, you may need to take medication or adjust your medication dosage.

Remember, you're not in this alone. Your diabetes treatment team is there to help you manage your diabetes. Work together to make sure you're doing everything you can to prevent diabetes complications.

Last Updated: 2010-03-11
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