Most people are shown how to use a blood glucose meter once, at diagnosis, and never again. Then a reading comes back oddly high or low, and there's no way to tell whether that's real or a technique problem.
Technique matters more than people expect. A dirty finger or a squeezed fingertip can shift a reading enough to change a treatment decision. Here's how to get it right, and the mistakes worth knowing about.
What you need
- A blood glucose meter
- Test strips that match your meter, they are not interchangeable between brands
- A lancing device and lancets
- A sharps container for used lancets
The steps
1. Wash your hands with warm soapy water and dry them properly. This is the step people skip and it causes more bad readings than anything else. Traces of food on the fingers, fruit especially, can push a reading dramatically high. Warm water also improves blood flow, which makes the next steps easier.
If you can't wash, an alcohol swab works, but let it dry completely before pricking. Wet alcohol on the skin dilutes the sample.
2. Insert the test strip into the meter. On modern meters the strip goes in first and the meter powers up ready. Check the strip is the right type and seated properly.
3. Set your lancing device depth. Most devices have adjustable depth settings. Thicker or calloused skin needs a deeper setting, thinner skin needs less. Start shallow and increase only if you aren't getting enough blood. Going deeper than necessary just hurts more.
4. Prick the side of your fingertip, not the pad. The pad is where the nerve endings are concentrated, the sides have fewer and hurt noticeably less. The World Health Organization suggests the middle and ring fingers give the best results.
Point your hand downward, below heart level, before pricking. Gravity does most of the work of getting a drop to form.
5. Don't squeeze. If you have to force blood out by squeezing the fingertip hard, you push interstitial fluid into the sample and dilute it, which skews the reading low. If a drop won't form, warm your hands, let the arm hang down, and try a deeper lancet setting next time rather than squeezing harder.
Gentle massage from the base of the finger toward the tip is fine. Hard squeezing at the puncture site is not.
6. Apply the drop to the strip. Hold the strip to the blood and let it draw the sample in. Only the blood should touch the strip, not your skin. Make sure the strip fills completely, an underfilled strip can read low or error out.
7. Read and record. Most meters give a result in about 5 seconds. Record it, either in the meter's memory, an app, or a notebook. Patterns over weeks are what your doctor or diabetes educator actually needs, not a single number.
8. Dispose of the lancet in a sharps container. Not the bin. Lancets are single use, a reused lancet is blunt, which hurts more and increases infection risk.
Mistakes that skew readings
Unwashed hands. Worth repeating because it's the biggest one. If you have just handled food, your reading can be wildly wrong.
Expired or badly stored strips. The enzyme on the strip degrades. Strips typically have a use by date, and once a vial is opened there is usually a shorter window, often around six months, marked on the label. Heat and humidity accelerate the breakdown, so a vial left in a hot car in an Australian summer may be unreliable well before its printed date. Keep the vial sealed and out of the bathroom, where humidity is high.
A cold meter. Meters have an operating temperature range. A meter that has been in a cold car or direct sun may read inaccurately or refuse to run until it equilibrates.
Reusing lancets. Blunt lancets tear rather than pierce, which hurts and makes calluses form faster.
Testing the same spot every time. Rotate fingers and sites. Repeated pricking in one place builds callus, which then makes it harder to get blood, which leads to deeper settings and more pain.
Wrong strips for the meter. Strips are meter specific. Sinocare Safe AQ Pro I strips work with the Safe AQ Pro I meter, not with another brand's device.
Checking your meter is accurate
Two ways worth knowing about.
Control solution. A liquid with a known glucose concentration that you test like a blood sample. If the result falls in the range printed on the strip vial, the meter and strips are working together correctly. Worth doing when you open a new vial of strips, if you drop the meter, or any time a reading looks implausible.
Compare against a lab test. Next time you have blood drawn at a pathology lab, do a finger prick on your own meter at the same time. Home meters are not lab instruments and some variation is expected, so discuss what an acceptable difference looks like with your doctor rather than assuming a mismatch means a broken meter.
Meter features that reduce error
Some sources of error are designed out rather than managed. Two worth understanding.
No coding. Older meters required you to enter a code matching each new vial of strips. Get it wrong or forget, and readings are off. Meters that code automatically remove that failure point entirely. The Safe AQ Pro I is a no coding meter.
Haematocrit range. Haematocrit is the proportion of blood made up of red blood cells, and it affects meter accuracy. Many meters are validated only across a typical adult range. That matters if you are testing a child, an elderly person with anaemia, or anyone whose blood concentration sits outside the usual range. The Safe AQ Pro I is validated across 10% to 70% haematocrit, wider than many consumer meters.
When a reading doesn't match how you feel
If you feel hypoglycaemic but the meter reads normal, or you feel fine and the meter reads alarmingly high, treat the symptoms as the more important signal and retest with clean hands and a fresh strip. Persistent mismatches are worth raising with your diabetes health professional rather than working around.
What we stock
Deciding between finger prick testing and continuous monitoring? Read our guide to blood glucose monitors vs CGM, or our comparison against Freestyle Libre and Dexcom.
Questions about equipment? Contact us at joe@novabiomedical.com.au or 1300 723 900.
General information about testing technique only, not medical advice. Your target blood glucose range, how often to test, and what to do about a result are clinical decisions set by your doctor or credentialled diabetes educator. If you are experiencing symptoms of severe hypoglycaemia or hyperglycaemia, seek medical attention. In an emergency, call 000.