Glucose Testing | Phlebotomist Report

I have pricked patients’ fingers to obtain blood for testing glucose as well as drawn blood from individuals’ veins for glucose tests.

While glucose is the analyte tested in both methods, the fingerstick method is quite different from drawing blood from a vein.

According to studies done, glucose levels found in capillary (fingerstick) and venous blood are slightly different. The differences, though, are not huge. Glucose levels in plasma (venous blood) tend to be higher than glucose levels in whole blood (capillary blood).

So, what are the differences between fingerstick and venipuncture for glucose? There are several of them, continue reading to find out.

Fingerstick Blood Test (Glucose)

The fingerstick blood test is simple to perform and within a minute or so you can know your sugar level. Here are the tools needed for doing a fingerstick for glucose:

Glucometer (instrument for testing glucose)

Strips (contain the reagents)

Lancet (needle to prick finger)

Lancet holder

Cotton balls (used to apply to site)

Alcohol swabs (used to clean the area)

How the procedure is done

The phlebotomist or trained individual will chose a finger. Then he/she will clean it with an alcohol swab. The tip or side of the finger will be allowed to air dry, after which, the lancet is used to prick the finger. Blood flowing out of the finger is placed unto the glucose strip. When done a cotton ball is placed on the site to stop blood flow. Seconds later the glucometer will give a reading.

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Venipuncture for Glucose

Venous blood test for glucose is a longer process. It could take anywhere from 3 to 5 minutes or even longer to obtain blood and then the sample has to be sent to the lab for testing which could take more than 24 hours to get the results.

More tools are needed for drawing blood from a vein. Here are several of them:

Tourniquet (to help find vein and make it palpable)

Alcohol swabs (to clean venipuncture site)

Cotton balls (to stop blood flow after venipuncture)

Adhesive bandage/plaster (to place over site)

Method for drawing blood (syringe, evacuated tube system, butterfly)

Needles (used with method)

Tubes (for blood collection)

Writing device (to write the patient’s name on the tube)

How the procedure is done

The phlebotomist places the tourniquet on the patient’s arm, then chooses a vein for venipuncture. The site is then cleaned with alcohol and left to air dry for about 30 seconds, after which, the needle is inserted into the vein and blood is drawn. When done, the tourniquet is released and the needle is removed from the vein and discarded. A cotton ball is used to apply pressure to the site to stop blood flow. After, a plaster is place on the site to protect it.

The sample is put in a suitable container or package and sent to the lab for testing.

Venous Blood Vs. Capillary Blood (fingerstick)

When drawing blood from a vein for glucose tests, more blood is collected than doing a fingerstick. A grey top is used to collect the blood. An anticoagulant in the tube prevents the blood from clotting, leaving it as whole blood.

The grey top is put to spin in a centrifuge for about 15 minutes. Then the plasma, the liquid portion of the blood is used for testing glucose. A small amount is taken and put in a machine to process. A few minutes later, glucose results are shown.

With a fingerstick, only a small amount of blood is needed to test for glucose. Whole blood from the person’s finger is placed onto the glucose strip, which contains reagents which react with the glucose in the blood to determine its value. Within a few seconds a reading is shown on the glucometer.

Why do Fingerstick for Glucose

Drawing blood from a person’s vein is the more traditional approach and has been done for many years. However, obtaining blood from a vein takes more time, tools, and uses bigger equipment. While venipuncture is reliable and trusted, the process is time consuming and longer.

Fingerstick blood test is more recent but it is easy, quick, and simple to do. It also takes less time and is fairly accurate. Glucometers are very convenient for those needing to check their glucose levels often, like diabetic patients. It also makes it easy for those who want to randomly check their sugar level or for basic screening.

At point-of-care testing places, fingerstick blood test is common and even employers may choose to do fingerstick blood test for employee health screening programs.

Is Fingerstick for Glucose Accurate?

Testing for glucose using the fingerstick method is accurate. Glucometers are very common and used widely around the world, especially by those who have been diagnosed with diabetes.

Glucose levels obtained using glucometers may differ slightly from venous blood levels but are not huge. Even repeating the same test at a laboratory doesn’t give you the same result. And also, results for the same test done at different labs are not the same.

Glucometer readings can be trusted, however, in times of doubt or if confirmation is needed, venous blood is used. Occasionally, the glucometer will not give a reading because the glucose is very high, which sometimes happens with diabetic patients. When that occurs a venous sample is obtained.

When to Choose Venipuncture Over Capillary Blood Test

The decision over which method to use is made by the doctor or the lab at which you did the blood test. Fingerstick is good for basic screening, random tests, and for monitoring sugar levels for diabetic patients.

However, if a person has to do many tests or is trying to figure out an health issue, venous blood test is the way to go.

For making changes in medications venous blood tests are also used.

Pros and Cons of Fingerstick for Glucose

While fingerstick for glucose is very convenient and easy to perform, it has its limitations. Here are some pros and cons of fingerstick for glucose test:

Pros:

Convenience. Fingerstick testing is a quick and convenient way to check blood glucose levels, and can be done anywhere, anytime.

Can be less painful than venipuncture. With modern lancets, when done properly, fingerstick testing can be relatively painless. Notwithstanding, it can also hurt as well.

Accurate. With proper technique and calibration, fingerstick testing can provide accurate glucose level readings.

Real-time results. Results are available almost immediately, allowing for prompt decisions by your healthcare provider.

Cons:

Slightly invasive. Fingerstick testing requires a small lancet to puncture the skin and obtain a drop of blood, which can be uncomfortable or distressing for some individuals.

Limited blood sample. Fingerstick testing requires only a small amount of blood, which can be a disadvantage in situations where larger blood samples are needed for diagnostic purposes.

Possible inaccuracy. The accuracy of fingerstick testing may be affected by factors such as poor technique, poor calibration, exposure of strips to light, exposure of strips to humidity and temperature, or improper handling of test strips.

Not continuous. Fingerstick testing only provides a snapshot of blood glucose levels at the time of testing, and cannot provide a continuous, real-time picture of glucose levels over an extended period.

Variability. Fingerstick testing can be subject to day-to-day variability, especially if the person’s diet or exercise patterns vary from day to day.

Pros and Cons of Venipuncture for Glucose

Venipuncture for glucose is time tested, reliable and the more accurate method between the two. However, it has its own drawbacks. Here are some pros and cons of venipuncture for glucose: