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Can Diabetes Blood Tests Give False Negative Results?

Discussion in 'Ask A Question' started by witloof, Jul 30, 2018.

  1. witloof

    witloof Prefer not to say · Newbie

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    I've been peeing a lot recently and one of the things my doctor has done has been to get me a blood test and a urine test for diabetes, and these turned out negative. The thing I am worried about is that in the week or two preceding the test (I was on holiday, so I couldn't get it done immediately), since I was already worried about diabetes and I wanted to pee less, I ate a lot less sugar than I normally do. Could this have brought my blood sugar down to less than it would normally have been, thus potentially hiding a diabetes problem by producing false negative results? I'm still trying to work out why sometimes I need to pee very frequently and other times I don't need to pee as often, and I'm still wondering whether that is connected with what I'm eating.

    I know that I tend to suffer from health anxiety, so it is hard for me to know whether this really is a question worth asking, or whether it's my anxiety playing tricks on me before I go to the doctor again.
     
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  2. Rachox

    Rachox Type 2 (in remission!) · Moderator
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    Hi witloof. Do you know what the test for Diabetes was that you had done? I think it would probably be an HbA1c, that’s the commonly used test these days. It’s a clever test that measures excess sugar stuck on your red blood cells. As your red blood cells live for up to twelve weeks the glucose measurement is a long term one. Your changing your eating habits in the week or two leading up to your test will have had little effect on the result.
    It sounds like you need to go back to your GP and clarify this and tell him/her about your anxieties.
     
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  3. witloof

    witloof Prefer not to say · Newbie

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    Thank you, Rachox. I don't know which test it was. I've just got the numbers. It's 100 mg/dL, which the lab results says is within the healthy range of 60-110. However I've just been doing a bit or reading and it seems that some countries and organisations consider 100 to be just inside the range for prediabetic. I'm not sure what to make of this.
     
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  4. LooperCat

    LooperCat Type 1 · Expert

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    That sounds like a fasting or random blood test, rather than an HbA1c. So a snapshot of exactly what's going on there and then - the same test we all take every time we prick our fingers at home.
     
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  5. Rachox

    Rachox Type 2 (in remission!) · Moderator
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    I don’t know where you are but you need to be guided by the guidelines where you are I guess, I think maybe by the units of your results that you aren’t in the U.K.
     
  6. Kittycat_7_

    Kittycat_7_ Type 2 · Well-Known Member

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    Hi,
    If your urinating lots you might have an urine infection, did the dr check your urine with a dipstick. Diabetes shows up as glucose and sometimes ketones in the urine.
    Are you feeling tired and thirsty? Please go back to your dr as your still not better.
    Hope you feel better very soon
    Take care
     
  7. Bluetit1802

    Bluetit1802 Type 2 (in remission!) · Legend

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    @witloof

    The HbA1c test can be very unreliable in people with non-standard red blood cells. This includes anaemia, but also includes people whose red blood cells live longer than the standard 120 days (the 120 days is only an average). If your RBC are long lived, your HbA1c will be higher than expected. Likewise, if your red blood cells live a lot less than 120 days, the HbA1c will be lower than expected. There can also be other haemoglobin variances.

    I have personal experience of this. Have a look at my thread here. https://www.diabetes.co.uk/forum/threads/2-hba1cs-2-labs-1-blood-sample.154627/
     
  8. NoCrbs4Me

    NoCrbs4Me I reversed my Type 2 · Well-Known Member

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    The 100 mg/dl result sounds like a fasting blood glucose test, not an HbA1c test.
     
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  9. Mbaker

    Mbaker Type 2 (in remission!) · Well-Known Member

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    100 mg/dl equates to 5.5 mmol if this was a fasting blood glucose test. If this was fasting it depends how you look at it. For a Type 2 who is attempting to get remission, this would be well on the way to a good position, otherwise it is a high normal; given what I know now with this figure I would consider some small lifestyle changes whilst getting acquainted with the number and other numbers over a period of months. Small changes could be a look at carb content, reduction of snacks and maybe some some walking after meals.
     
  10. Crocodile

    Crocodile Type 2 · Well-Known Member

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    Spot test is useless. It just gives a picture of what the level is at the time. Everybody is slightly different but unlikely that prediabetes would directly cause excessive piddling for T2. This usually occurs when the sugar levels are so high that any form of moisture in the body is directed to the kidneys just to maintain clearance rates. The classic symptom of excessive thirst results and the tell tale sign of drink lots, pee lots. Glucose levels continue to climb when the clearance rate can't keep up with what you stick in your belly. Not sure what happens with T1.
     
  11. Bluetit1802

    Bluetit1802 Type 2 (in remission!) · Legend

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    Yes, you are quite right. I was having a very senior moment :arghh:
     
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