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Diabetes: Blood Sugar Testing at Home

Why is blood sugar testing important?

Measuring blood sugar (glucose) levels at home has become a cornerstone of diabetes care. Measuring your blood sugar regularly can:

  • Help you know if your blood sugar is within your target range. Staying in a healthy range can help prevent or delay the long-term complications of high blood sugar, such as heart, kidney, eye, nerve, and circulation problems.
  • Help you know if your blood sugar is too low or too high and treatment is needed.
  • Help you know how much and which type of insulin to use.
  • Prevent low blood sugar at night.
  • Help you manage illness at home.
  • Let you know if you need to do a ketone test.
  • Help you understand the effects of certain foods, exercise, and stress on your blood sugar.
  • Help your healthcare provider know if changes in your treatment are needed.

For most people blood sugar testing has replaced testing their urine for sugar. This is because urine testing gives only a rough idea of the blood sugar level. Urine tests do not tell you what your blood sugar is at the moment you do the test. They also cannot tell you if your blood sugar is too low. Sugar usually does not show in the urine until blood sugar is at least 180 milligrams per deciliter (mg/dL).

What supplies are needed?

Doing a blood test requires:

  • a way to prick the skin to get a drop of blood
  • a way to read the results

Finger-pricking (lancing) device: A finger-pricking device (called a lancet) is used to get the drop of blood. The lancet can often be set at different depths for different people. Adjustable lancets are good for tender skin and for when you do not need the lancet to go deep. Remember to change the lancet every day. A sharp and clean lancet helps prevent injury and infection.

Blood glucose meter (glucometer): Most people use blood glucose meters to test their blood sugar. If meters are not available, color-changing blood sugar strips may be used. Not all meters measure in the same way, so the results from different meters are not always the same. It doesn't matter which type of meter you choose as long as you always use the same meter. Bring your meter to each clinic visit. Your healthcare provider will want to see the information from the meter.

Some features to look for in a meter include:

  • accuracy (make sure the meter is accurate in the environment in which you live, for example, cool or hot temperatures, high humidity, or high altitude)
  • ability to store at least the last 100 test values (to share with your healthcare provider at your checkups)
  • small size for easy carrying
  • quick testing time
  • ability to check meter accuracy with a control solution or strip

Test strips: When choosing test strips, make sure they work in the meter you are using. Look for strips that need only a small drop of blood and can draw the blood into the strip. The glucose strips usually cost about $2 to $3 per day, so insurance coverage is important if it is available. Make sure you know what types of strips your insurance will pay for before you choose your meter.

Different meters have different instructions so it is important to learn how to test using your meter. It is best to have your provider, diabetes educator, or pharmacist show you how to use your meter. Then, test your blood sugar in front of them so they can check that you are doing it correctly. It is also a good idea to have family members learn how to test your blood

How do I do a blood sugar test?

To get a drop of blood from a finger:

  1. Wash your hands with warm water. This increases blood flow and makes sure there is nothing on the finger that may change the reading. Do not routinely wipe the finger with alcohol. Any trace of alcohol left on the skin will interfere with the test. Occasionally, when you are away from home (for example, camping or picnics), you may need to use alcohol-free travel wipes to clean the area. If alcohol wipes are the only cleaner available, be sure to let the alcohol dry completely before pricking your finger.
  2. Air dry the area before pricking.
  3. Use the lancet to prick the side of the finger rather than the fleshy pad on the fingertip (which is more painful). It is often helpful to place the finger on a table. This helps prevent the natural reflex of withdrawing the finger when poked. If the drop is not coming easily, hold the hand down to the side of the body to increase the blood flow to the finger.
  4. Put the drop of blood on the strip. (If a test strip has been in a cooler or refrigerator, bring it to room temperature before using.) Make sure you completely cover the required area on the strip with blood. Putting too small a drop on the strip is one of the most common errors.
  5. Use your blood glucose meter to measure the sugar level from the strip. If you are using color-changing strips, compare the color to the color chart on the package at the appropriate time. You will have to use a watch with a secondhand and be careful to check the level after the exact amount of time required according to the package directions.

Avoid inaccurate (wrong) blood sugar results by making sure:

  • Your meter is clean.
  • The test strip is not outdated.
  • The meter is set up for the current box of test strips.
  • The meter and test strip are at room temperature.
  • Your blood drop is large enough.

Do I have to prick a finger?

You can prick other parts of your body instead of a finger. Pricking other sites may not hurt as much. The most common alternate site is the forearm. Other places to test include the fleshy part of the hand, upper arm, thigh, and back of the calf. The lancet blade or needle must be dialed to the maximum depth to get enough blood from these sites. Make sure you have a meter that works for these testing sites.

The main problem with not using the fingertips is that the blood flow through the arm is slower than through the fingers. The slower blood flow means the blood sugar value from the arm is 10 minutes behind the blood sugar value in the fingertip. If you are going to prick another site, such as your arm, rub the site before pricking. Rubbing increases blood flow in the area. If you are having symptoms of low blood sugar, prick your fingertip. It’s faster and you will know what your blood sugar level is more quickly.

There are ways to stick your finger that are less painful. For example, you can try:

  • using a lancet device at a low setting
  • aiming for the side of the fingertip
  • not using alcohol or making sure it is dry before sticking yourself

Also, washing your hands in warm water (and then drying them well) makes it easier to get a good drop of blood.

A continuous glucose monitor may be useful if you take frequent insulin doses to keep your blood sugar in a very narrow range. These devices sense blood sugar under the skin and display the reading on a screen. They can also be set to sound an alarm when blood sugar reaches a certain low or high point.

When should I do a blood sugar test?

In general, your healthcare provider will tell you when and how often you need to check your blood sugar. When you have just been diagnosed with diabetes you will need to check your blood sugar more often. After you have your diabetes under control, your provider will tell you how you can decrease your sugar checks.

Some common testing times include first thing in the morning, before meals, before driving, at bedtime, and any time you feel like your blood sugar may be too high or too low. You should check your blood sugar when you are feeling ill.

If you take insulin more than once a day or use an insulin pump, the American Diabetes Association (ADA) recommends testing 3 or more times a day.

You may need to test more often when your insulin type or dose has recently changed.

What should the blood sugar level be?

The desired blood sugar levels at different times are:

  • Fasting or before meals: 70 to 130 milligrams per deciliter (mg/dL), or 3.9 to 7.2 millimoles per liter (mmol/L)
  • After meals: less than 180 mg/dL, or 10 mmol/L (1 to 2 hours after the time you started a meal)
  • Bedtime: 100 to 140 mg/dL, or 5.5 to 7.8 mmol/L

The American Diabetic Association recommends a blood sugar of 70 to 130 when you are fasting or before meals. However, some people start having symptoms of low blood sugar at a blood sugar below 90 mg/dL (5 mmol/L). Ask your provider what upper and lower blood sugar goals he or she recommends for you. Also ask your provider to write down what you should do if your blood sugar result is too high or too low.

Should I keep written records?

Keeping good records to look for patterns in blood sugars is essential. It is wise to keep written records even if your meter is able to store results (in case the meter breaks). Write down the time of the test, the date, how you feel, and the blood sugar value. You may also want to note when you exercised, were sick, or felt stressed. It may be helpful to record what you ate for a bedtime snack or any evening exercise to see if these are related to morning blood sugars. Also, keep a record of when you have low blood sugar reactions and what you think the possible causes were. Always take your blood sugar records to checkups with your healthcare provider. You can then share this diary with your provider or diabetes educator and they can help you learn what changes your blood sugar, and this will help you control it better.

Abstracted from the book, "Understanding Diabetes," 10th Edition, by H. Peter Chase, MD (available by calling 1-800-695-2873).
Published by RelayHealth.
Last modified: 2011-07-28
Last reviewed: 2011-03-03
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
© 2011 RelayHealth and/or its affiliates. All rights reserved.
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