Monitoring Your Blood

finger stick test

Check your glucose throughout the day.

There are many brands and models of glucose meters. All of them test blood sugar levels with a drop of blood obtained from your fingertips.

The only way to get a “snapshot” of  your blood glucose level is to use your blood glucose meter or continuous glucose sensor.

In this section, you will learn about:

When to Monitor

To find out how your blood glucose specifically responds to your treatment plan, check your blood glucose at different times throughout the day. Good times to check include before and after meals, and whenever you feel “low” or sense that your blood sugar may be off target. Blood sugar checks also are a good idea when you are sick or changing activity. Ask your medical provider to recommend the blood glucose monitoring schedule that best fits your needs.


Glucose meters

All glucose meters test blood sugar levels with a drop of blood obtained from your fingertips. Some meters also are approved to test blood obtained from alternative sites.

Fingerstick Testing Glucose Meters

There are many brands and models, which vary in price and features. Different health insurance plans may limit coverage to specific models, and may limit the number of test strips that will be supplied.

Each meter needs a blood sample that is usually obtained by pricking your finger with a lancing device. The sample is placed on a test strip that has been inserted into the meter and analyzed by the meter.

Fingerstick and Alternative Site Testing Glucose Meters

Some meters are approved for both fingerstick and alternative sites testing, which means poking your skin somewhere else on your body other than your fingertip for a blood sample. Alternative site testing may lag behind fingerstick testing by 20 minutes or more. Alternative site testing results are similar to fingerstick testing results only when the blood sugar is steady and not moving rapidly up or rapidly down.

For example, after eating, your blood sugar may be rapidly rising, and the alternative site testing may give a blood sugar result that is erroneously low. Conversely, after exercising, your blood sugar may be falling, and alternative site testing may give a result that is misleadingly high. These incorrect results can result in making the wrong decision such as not eating a carbohydrate containing snack when you blood sugar is low, or not taking other corrective action.

Fingerstick testing is still the most accurate reflection of sugar levels in the blood stream.

It’s a good idea to discuss meter selection with your health care provider or diabetes educator. Do not share your lancet or meter with anyone else. Register your meter with the manufacturer so that you can be notified if there is any product recall.

Accuracy Always

  • Read the directions that come with your glucose meter.
  • Keep the strips in the original capped container. Light and air can damage them.
  • Be sure your test strips are not outdated
  • Re-calibrate your meter each time you open a new canister of strips
  • Retain the help-line telephone number provided by the manufacturer.

How to use your glucose meter:

  1. Wash and dry your hands
  2. Insert test strip into meter
  3. Prick your fingertip with a lancing device
  4. Apply blood sample to the test strip
  5. Read result
  6. Record result in your log

Continuous Glucose Monitors

Continuous Glucose Monitors (CGM) are devices that measure glucose in body fluids between cells (also known as interstitial fluid); they do not directly measure the blood glucose.

The devices are set in place by you the user and changed every few days to a week or more. Most sensors are taped to the skin and a probe passes through the skin into fatty tissue where it analyzes sugar levels in the fluid between the cells. The sensors continuously collect samples from under the skin and transmit the data to a receiver. Every 1-5 minutes, the receiver displays a glucose reading which is an average of these samples. The receiver also shows glucose trends and can be programmed to sound an alarm if the glucose level gets too high or too low.

Continuous glucose monitors can help you achieve your target blood glucose control

  • The Alarms for high and low blood sugars and trend alarms allow earlier intervention and help you prevent more severe highs and lows.
  • The 24 hour trend data helps fine tune diabetes or insulin dosing algorithms
  • Use of these devices improves blood glucose control because you can minimize the time spent with high or low blood sugars

But remember:

  • The glucose level obtained with CGM may lag behind a blood glucose level by 5 to 25 minutes. The levels may not be the same as those obtained with a blood glucose meter.
  • CGM still have to be calibrated or reconciled with blood glucose readings obtained with a blood glucose meter. So you still have to do fingerstick glucose monitoring
  • And most important, before you even consider any treatment changes, you will need to do traditional blood glucose testing to verify a glucose level determined by a CGMS device. The continuous glucose monitor results have to be verified before you change your therapy.

There are several continuous sensors on the market. Here are some questions you will need to consider:

  • Sensor life: How long does the sensor last?
  • Where on the body is the sensor worn or inserted?
  • How are the sensor and receiver connected?
  • How big is the sensor and receiver?
  • Does the sensor have the ability to link the glucose results directly to an insulin pump (continuous subcutaneous insulin infusion – CSII)?
  • How much does it cost and how much will be covered by medical insurance?
  • How accurate are the glucose results?
  • How are the glucose levels displayed and is the display easy to read?
  • How complicated is it to understand the technical aspects of the device?
  • Is the sensor comfortable?

Tips for Good Monitoring

  • Monitor your glucose levels frequently when you change your routine, and this includes everything from trying new foods, new form of exercise, when you are sick, stressed, traveling, or changing medications.
  • Know the limitations of alternative site testing and continuous glucose monitors. Finger tip blood glucose monitoring still provides the most accurate reflection of sugar levels in the blood stream. Blood samples from other, non-finger tip sites may not be “real time” as they lag behind the blood sugar found in finger-tip blood. This means that if your blood sugar is falling quickly, the results from the alternative site may be higher than the blood sugar really is. The converse also is true. If the blood sugar is rising, the alternative site reading can be misleadingly low. Do NOT use alternate site testing if your blood sugar is rising or falling quickly, you suspect you have a  low blood glucoseor if you have hypoglycemic unawareness.
  • Verify continuous glucose monitoring sensor results with a fingerstick glucose test before making any acute change in your therapy. For example, if your continuous glucose monitoring device gives a high glucose result, double check with a finger stick test before taking extra insulin or diabetes medication. Conversely, if the sensor glucose value is low, validate the result with a fingerstick test before eating additional carbohydrate containing snacks or reducing your diabetes medication or insulin dose.
  • Keep your monitoring equipment with you at all times. It’s important to be able to check your blood sugar if you feel low, or are unsure. Guessing is unwise and risky. This is especially true if you are engaged in activities that require your full attention and coordination, such as driving or playing sports, or at work, where the safe performance of your job – construction being one example – requires alertness at all times.

Vigilant monitoring of your blood sugar is essential to your health.

Self-assessment Quiz

Self assessment quizzes are available for topics covered in this website. To find out how much you have learned about  Monitoring Your Diabetes, take our self assessment quiz when you have completed this section.  The quiz is multiple choice. Please choose the single best answer to each question. At the end of the quiz, your score will display. If your score is over 70% correct, you are doing very well. If your score is less than 70%, you can return to this section and review the information.

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