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False positive tests vs 2 glucose monitors


During a yearly check-up, my bloodwork showed higher than average glucose levels (7.1). I was then asked to take a GTT ( 2 hour) and the lab results came back as 10.8!

My husband is a Type 2, uses insulin and has glucose monitors. They do appear to be working. So, for the past 4 weeks I have been taking morning readings and after meal readings and they are in the 4-6 range which I gather is normal. The A1c test registered 5.6. My GP is convinced I have diabetes and when I did a follow-up appointment and showed her my levels that I put on a spreadsheet, she said she didn't have time and dismissed my concerns and queries. She wanted to put me on Metformin even before the A1c.

Is it possible that the first two tests were wrong? I have another appointment with a new GP who was highly recommended to me and I would like a second opinion. It is not that I am in denial, more like the lab findings and the weekly/daily readings tell me something otherwise. This is rather perplexing.

Anyone else have this experience? I suppose I would rather this scenario be a proverbial wake-up call than something definitive for the time being.

Thank you.
14 Responses
Avatar universal
Hi Adelaide,
There are many people on here who are very knowledgeable and make say more to help you.  I will just give you my 2 cents. You  absolutely did the right thing by going to a 2nd doc. I do not have diabetes, however I'm an RN. It is vitally important that you get a correct diagnoses. As you must know Diabetes is nothing to fool around with. Glucose monitors are not your most reliable source, especially if you don't do the required quality controls.  I'm not putting them down, but the blood drawn at the lab value is more reliable. Also, you should have fasted the night before. NOTHING to eat or drink except water. Good luck in your endeavor you will get a correct result if you follow what I have just told you. the 2hr GTT test is very good anf forget that first doc who didn't have time to be bothered.
Avatar universal
I definitely agree that a doctor who "doesn't have time" to listen to you is not a good doctor for you. I'm a little confused about your numbers, especially since you use the Canadian numbers and it's easy to confuse them with A1Cs. What type of test was the 7.1? Was that an A1C or a fasting blood sugar. If the latter, yes 7.1 (127.8) fasting is just into the diabetic range. (126) The OGTT is just under the definition of diabetes (200). The 10.8 is 194.4 and makes it pre-diabetic. However the A1C you report 5.6 is under even the pre-diabetes level (starting at 5.7). The A1C is the standard for diagnosis of pre-diabetes and diabetes. So what I see in these numbers and the ones you report at home is that something is happening for sure but a diagnosis of full diabetes (rather than pre-diabetes) might be premature. If you have pre-diabetes you might want to start by trying to control it with reduction of carbs, exercise and weight loss if needed. For many people (not all) this will keep the pre-diabetes from advancing.
141598 tn?1355675363
Yes, definitely run as fast as you can from your previous doctor and get retested at the new doctors office. An OGTT [GTT] to me is a waste of time and should rarely be used. Get a fasting plasma glucose test because this test is simpler, more accurate, less expensive, and less variable than the OGTT.

Normal fasting range = 3.3-5.5 mmol/l <---where you want be
Prediabetes range = 5.6-6.9 mmol/l

Include in the same blood draw [sample] an A1c test then use this formula to see your estimated daily average glucose [eAG] as compared to your fasting glucose results level.

28.7 X A1c – 46.7 = eAG
Then divide by 18 or multiply by 0.055 to see your mmol/l results.

A1c normal range = <4.9%
A1c prediabetes = 4.9-5.5% [5.6-6.9 mmol/l]

Avatar universal
Actually for purposes of diagnosis (for which it is now the test of choice), A1c of 5.7-6.4 is considered pre-diabetes and 6.5 and over is diabetes.
231441 tn?1333896366
Another comment:  if you are indeed prediabetic, metformin may not necessarily be a bad choice, combined with diet and exercise measures.  Together they may keep things stable for a long time.

However, it is right to look into this closely.  You don't want a diagnosis of diabetes if you don't have it.

141598 tn?1355675363
"A1c of 5.7-6.4 is considered pre-diabetes and 6.5 and over is diabetes."

I used the ADA [American Diabetes Association] eAG online calculator for the following:

The equivalent of 5.7% A1C is  6.5 mmol/l eAG. [117 mg/dl]
The equivalent of 6.4% A1C is 7.6 mmol/l eAG. [137 mg/dl]

Prediabetes range
The equivalent of 5.1% A1C is 5.5 mmol/l eAG. [100 mg/dl]
The equivalent of 6% A1C is 7.0 mmol/l eAG. [126 mg/dl]

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231441 tn?1333896366
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