Meter Accuracy

Two things landed on my desk recently. One was a newspaper article saying that the Food and Drug Administration has asked the international body that sets standards for home blood glucose meters to tighten its accuracy requirements. (A public meeting on the topic is scheduled for March 16 and 17.) The other was a letter from a Diabetes Self-Management subscriber who described how she had attempted to compare two home meters with a plasma glucose measurement done in a laboratory — and how she was unnerved when she got three different readings.


Stricter standards for meter accuracy would be a welcome development: Currently, most available blood glucose meters are accurate only to within 10% to 15% of the actual blood glucose level. But it will likely be a while before standards are changed and more accurate meters become the norm.

In the meantime, there are steps you can take to get the best possible results from your meter. One of the most important is to use only strips made for your meter and to use them correctly. This includes making sure the strips have not passed their expiration date, coding your meter for each new batch of strips (if you use a meter that requires coding), and being careful to store your strips in their original container, away from sources of heat, cold, or humidity. Improperly used or stored strips are one of the biggest sources of error in home blood glucose monitoring. To check whether a batch of strips is OK, use a drop of the control solution (unexpired!) that’s compatible with your meter on one of the strips in the batch.

If you still want to check the accuracy of your meter by comparing it to a laboratory measurement, there is a way to do that. But getting meaningful results requires doing it right — both on your end and on the laboratory’s.

To explain how to do it right, I asked diabetes nurse specialist and DSM Editorial Board member Virginia Peragallo-Dittko to update some instructions she’d written for the magazine back in 2000, and here are the results:

Comparing Your Meter With the Lab

The best way to determine whether your meter readings are accurate is to test them against the results you get from a laboratory. The advanced equipment in a lab allows technicians to make exact measurements. Don’t bother comparing your meter to another home meter; neither system is considered a laboratory standard. If your self-monitoring results match the ones you get from the lab, you’ll know they’re accurate. If not, consult your diabetes educator, who can help you figure out what the problem is.

To compare meter and lab results, the two tests must be done at the same time. In addition, you must do the comparison with a fasting blood glucose sample. After-meal readings will differ between capillary blood (used by your meter) and venous blood (used in the lab).

Before any blood is drawn, if you use a meter that needs to be coded to the numbered lot of strips, double-check that the code is correct. In addition, use a drop of control solution on your meter’s test strip so you are sure that your test strips are not damaged.

Once you and the technician are ready, perform a fingerstick check just prior to having blood drawn from your arm. (Doing the fingerstick after the blood is drawn from your arm is impractical since you may have to hold gauze to your arm after the venipuncture.) Doing a fingerstick at home either before or after the venipuncture allows too much time between the readings for a valid comparison.

Use a blood sample from your fingertip only for your meter reading. Do not use blood from an alternative site such as your forearm, thigh, palm, or upper arm. Meter readings from these sites are not always identical to fingertip readings. Similarly, if the lab technician offers to place a drop of blood from the venipuncture needle onto your meter strip, don’t accept the offer. Some strips are designed for capillary blood only and will give false results if the venous blood is used.

For the purposes of comparison, the venous blood that was collected into a tube must be spun by a centrifuge machine to separate the red blood cells from the plasma within 30 minutes after the time the blood sample was taken. If it is not, the glucose in the blood will begin to break down, and the results will not accurately reflect the blood glucose levels at the time the sample was collected. (Note, however, that even if the sample is not centrifuged within 30 minutes, the results are still good enough to diagnose diabetes or to alert your health-care provider to a problem with your diabetes control.)

Although you have no direct control over when the specimen is centrifuged, you can ask the lab technician about the time frame and request that it be done within 30 minutes. Explain that you are trying to assess the accuracy of your meter and that centrifuging within 30 minutes is a critical component of making that comparison. If the lab can assure you that centrifuging will be done within 30 minutes of the blood draw, you will have a valid comparison. If it cannot, you should not bother to compare the two results.

Assuming you get the necessary assurance from the lab, be sure to write down your meter reading and flag it somehow so you know which meter reading to compare to your lab result when you get it. Under current standards, your blood glucose meter is considered accurate if its results fall within 20% of the laboratory results.

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  • Steve Parker, M.D.

    When you say “within 20% of the lab’s result,” do you mean 20% either way?

    Example, if true actual value is 100 mg/dl. 20% above is 120 mg/dl; 20% below is 80 mg/dl. So your meter reading anywhere between 80 and 120 is considered accurate?

    If 20% above and below is the case, then a true value of 250 mg/dl could be metered out at either 200 or 300 mg/dl and still be accurate. (20% of 250 is 50.)

    OR example #2: True value is 100 mg/dl. Meter is “accurate” if it reads 90-110 mg/dl (20% of 100)? True value of 250 mg/dl could be metered at 225 or 275% (the range of 50 mg/dl is 20% of 250) and be “accurate.”

    Sorry I don’t quite understand. As you know, hospital nurses use portable meters quite commonly for inpatient diabetics. After a while, even doctors and nurses tend to believe the meters are more accurate than the reality. “174 mg/dl” sounds so definite.

    Here’s the silver lining to this cloud: It’s much better to have the meters than not. And technology 10 years from now will be better than it is today.


    • John Rummery

      Readings within one minute: 172, 154, 198 and 160, and ten minutes later 176: I just don’t believe it!

  • Calgarydiabetic

    The 5 second meters that are sold now are horrible. Plus or minus 20% kills diabetics. 10 years ago I had a 60 second meter that was always 5% below the lab results. now many results are outside the 20% and even worst they are not consistently above or below. the Govt shold force them to offer the old meters and test strips.

  • Ingrid Strauch

    Hi Steve,

    I’m looking into your question to make sure I get you a correct answer. In the meantime, however, remember that the “within 20%” statement refers to a comparison of capillary blood to venous blood. While the difference between the level of glucose in the blood in the capillaries and the level in the veins should be small after an eight-hour fast, a certain amount of difference is expected, just because of the way blood circulation works in the body.

  • Conrad G. Creitz

    “…readings will differ between capillary blood (used by your meter) and venous blood (used in the lab).” I believe that is the whole problem capillary blood vs. venous blood. There is no set standard for both the lab and meters at home. I think there should be a single standard control solution that works for all meters. They have done this with the A1C levels which are certified by National Glycohemoglobin Standardization Program (NGSP) and they should be able to do this with our blood glucose meters. Having a meter that is only within 20% accuracy results in many diabetics getting either an over-dose or an under-dose of insulin either or both could be serious problem for many diabetics.
    I seem to collect BG meters and now have 6 of them. In one case two of the meters were apart more than the 20% (meter a = 128 and meter b = 165), at a different time they both tested the same (102) in both cases the test came from a single finger stick and single drop of blood.

  • Helen M.

    I agree with Steve with respect to the old meters. I had one that was within 2 points of my serum draw. I took sliding scale lispro before a meal and was very stable with an A1C of 5.5-6.0.

    With the new meters my levels fluctuate wildly with frequent lows and highs. very hard to judge insulin amounts to give because of unreliability in readings. 1-2 units off and I’m in the pit or on the clouds….

    Why aren’t standards stricter? The medical community wants compliance of patients, but after a while we get tired of the ups and downs and give up and get burned out. What’s worse, I’m a nurse and see the frustration in my patients too.

  • Kurmie

    I’ve done side-by-side comparisons of meter readings of both different and identical meters and found no consistency whatsoever, even between identical models. What I do now is take a meter reading at the first sign of a low blood sugar incident, and use that number as a benchmark for future readings with that particular meter. I’ve found this number can vary from under 50 in one meter, while being near 70 in another, but knowing where my reading is relative to that number is more meaningful than just knowing my reading is 90. When a doctor or dentist asks me how my numbers are, I no longer quote meaningless meter readings, I tell him or her my last A1c number.

  • Bob

    This meter discussion now orientated toward telling the diabetic that their meter is best because you can obtain blood from some place other than fingers. My doctor wants readings from fingers as the most accurate reading. Also exposing the strip outside the container will effect the accuracy of the strip. I use the ACCU-CHEK COMPACT PLUS meter so I never touch or expose the strip and getting pretty accurate readings in comparison with the lab equipment.
    Also this meter results can be downloaded into a software complete with monthly listings and graphs if needed. I have been a Type 2 diabetic for 12 years.

  • Monte Nagy

    Hello all,
    Well now this get to be almost as confusing as politics. Variations of test results are common with my meter while testing capillary samples. tks for comments by all, now I’m really not happy with test procedures and equipment but its all I have.
    I can understand a 3%± variable but 20%???

  • Ludovico Horvath

    Can anybody tell me why do I have higher b.g.l
    readings when I clean my finger with alcohol swab,
    instead of soapy water? Thanks

  • Calgarydiabetic

    In the USA the meters are supposed to be calibrated to make the lab test and the meter reading the same. The 20% error does not have anything to do with that. It has a lot do do with the 5 second measurement time and possibly loose manufacturing standards for the test strips.

  • Mike

    I have tested the same blood drop from the same finger poke within seconds of each other and have come up with readings as much as 20% off. How is that possible?

  • Madge Alexander

    I am type 1 diabetic, and have always used the Lifescan meter, never any problems, always could depend on it for accurate readings (45 seconds to reading). Now, I can’t get strips for this meter any longer, and have had the unhappy experience of finding out that all the new meters are geared to “conveniency” (5 seconds), NOT accuracy. I have three other meters I purchased, and all of them are the same–at least 10-30-40 or more points higher than my trusty meter. What is the point of having a meter, if you can’t depend on it? I want accuracy, not conveniency–whoever designed these new meters does not know what they are doing–it’s a CRIME!! Somebody needs to wake up at the helm and design meters for ACCURACY!!

  • Diane

    I agree, wholeheartedly with all who are dissatisfied with the accuracy of their meter.

    And I, too, am about to just quit using the darn thing. I have no idea what my actual readings are, so how can it be useful, other than staying somewhere between 80 and 300?

    To whom should we be sending our suggestions and comments?

  • jim snell

    What is this? an excuse for more puff pastry.
    I see no mention of the fda issue on pqq test strip technology and how it has resulted in 13 death’s.

    20 per cent is a disgrace. i can live with at the meter level. at the strip level – nonsense. these should be graded into
    +/- 5 %. iam always throwing out strips and redoing.

    a also have another meter – non -pqq strip technology that is very sensitive to the water content – ie dehydration and I see 20 to 100 points off on readings. grab a couple of glasses of water and readings return to normal.

    my other meter using pqq strip technology is okay ntil i consume any food/liquid with any other alcohol sugars like malto dextrin and off wq go with readings off the map.

    i consider the present offerings and their 20% accuracy as being unnecessarily problematic.

    i am doing about 16 to 20 strips a day. maybe time for cgm

  • Genell Ryce

    I am retired,so medicare take care of my diabetes supplies.I was suprise that medicare only pays for one strip per day to test glucose reading, sometimes I need to test two or more times per day, it all depends on how I am feeling.I think that most meters are close to the lows and hights of your blood glucose. P.S. I heard from my health care providing team that this has something to do with my A1C numbers.As a retiree It seems I have to pay more for health maintenance. November 11 2010

  • Brian – Tx

    I have to agree with the group. I just got a Contour USB meter yesterday. I compared it to my TRUE TRACK (yep) and it reads consistantly 30 points below my True Track. I have been using both just to see how the Contour performed, but I ran out of True Track strips while at work. I took a reading with the Contour and it seemed high compared to how my vision was reacting ( I was able to see minute detail at the time, something I cant do when my readings are as high as the Contour was suggesting). I retested, and the reading was 50 points lower. So, I retested again and again, they were 50 points lower than the first reading. Good thing I decided to retest. I was about to take my insulin. It irks me that people die and the “industry” does nothing to improve their meters. Maybe a good heafty law suit would do the trick? Hummmmm…..

  • Tina

    The “International Organisation for standardisation” is for accuracy + or – 20% (40% total difference allowed). I just finished testing one of the meters tested in the following study, and got a 60 point difference with the same finger stick and same cannister of strips.

  • Jeanne

    This makes me feel a lot better, but doesn’t help me much. My last A1C was much higher than I expected based on my meter readings. I suspected my meter was the problem, so my doctor gave me a new brand to try. The results were 20-30 points higher on the new meter using the same sample of blood. Now I’m just not sure what my blood sugars are and how to correct for them. I wear an insulin pump, but don’t know how much to bolus. Exact, accurate blood sugar readings are critical for a diabetic. Does anyone recommend a particular meter over others? I cannot go by “how I feel”, that just won’t work. Glad to know others are having this problem, but sorry all of us are having this problem.

  • ronnie048

    I have tried a few of the meters on the market.precision ,true balance and bionime.Eventually I tried a true result meter (uses true test strips ) and was very satisfied with the results I got.It matched my clinical results which was much lower than that of the other meters I used before.
    When I compared with the testing solution true result read 47 on a 30-60 range which is around average. True balance read 117 on a 88-120 range,which was above average .

  • ruthav

    Jeanne (7/5/12) You should talk to your MD or your Diabetic Educator about looking into a meter that communicates with your pump. I use the OneTouch UltraLink and it has bluetooth technology that downloads my BG findings right into my pump. This allows the Wizard to calculate the amount of bolus I need without having to do the calculations each time. I find it very freeing. I have never had any issues with not taking enough or too much insulin as a result, as long as I calculate the correct number of carbs I am eating for each meal. You Educator or Pump Specialist can help you set up the Wizard.

  • John

    I had a prediabeties test done and my fasting glucose level was 91 mg/dL and my A1c was 5.6. The A1c got me worried after what I’d read online. So, I started using the True2Go meter. It’s been telling me that my fasting glucose level is as low as 70, which is a big diference from 91. One time I did a test 45 minutes after a breakfast of two eggs on a white roll and some white potato. My fasting level had been 87, but after eating the aforementioned breakfast, I got a reading of 149. I immediately did another test from the same blood drop and got 142. These may not be high for a diabetic. But, they’ve got me worried and I don’t know what to believe. I read that one’s blood glucose level shouldn’t go over 140 an hour after eating. But, these test reults tell me my blood glucose level could be anywhere from around 120 to as high as 170. How is this going to help me? Is my meter off? Am I safe? Should I get the testing solution? Should I see my doctor for a venous blood test?

  • sharon hoben

    I am so confused now . My insurance company stopped my last meter and sent me a new one. Now my readings are so off 20to 30 points from old meter. I didn’t think I had a problem with old meter?Or is it the new meter? Very confused at this point.

    • frustrated

      Same thing – my new insurance mandated brand is consistently 20-25 points higher than the brand I was using. Almost makes me think they purposely stopped covering the low reading one so people think they have a worse problem than they already have.

  • Kathryn Walker

    I saw my Endocrinologist the other day and told her that I was having trouble controlling my blood sugar. We discussed what to do if I have to take corticosteroids injected into joints for inflammation, or prednisone for my asthma. Both raise my BS very high. She advised me to continue using my sliding scale for my Humalog and keep my Lemeire at the same dosage as previously changed. She kept telling me to take one unit Humalog for each two points past my sliding scale maximum. I have no idea what “points” are and just thought I was misunderstanding her since I was not wearing my hearing aides, which without them I don’t understand all that is said even if I hear the word. What the heck does “point” mean? Please clarify this problem for me.

    Thank you,

  • Faisal Haroon Faisal

    It’s all confusing. Perhaps this is the essence of all knowlede- the more it is made complex the more highly it is valued in so far as its acceptance for analysis and discussion is concerned. The original question was as simple as there possibly can anything be. what does the variance of 20% mean? and the main topic linked it to the accuracy of an ordinary glucometre used by an ordinary and non-medical person at home.The question was if i check my glucose on an ordinary glucometer at home and it gives me the reading of 100, my actual blood sugar is 80 0r 120? or it is (80+120)/2=100. But none has given the simple answer instead every one has proved himself/herself more knowledgable than others. If, however, a meter tells 100 and it may be 120 or it may be 80, can anything on earth be more confusing than yhis. In this case the answer should have been the right place of all such glucometers is a Recycle Bin.