Help Understanding Blood Glucose Monitor Reading

[wildrose]

Hello Everyone,

I'm new to this forum and relatively new to diabetes and need some help understanding blood glucose monitors and their results.

In November 2013 I went for a health check and was told I was pre-diabetic. My FBS was 6.0 mmol/L and PPBS 8.39. I was told to eat better and get more exercise and check my blood sugar levels again in 3-6 months.

After 3 months of eating very healthily and exercising, I lost around 6kgs but was a normal weight before, I got my numbers down to FBS 5.8 and PPBS 6.5 and had a HbA1C test done with a result of 5.29%. I was really happy with these results and thought that continued healthy living might reduce the numbers further so I bought a OneTouch Select monitor to monitor my blood levels occasionally between hospital tests.

So far, my occasional at home testing has been positive and my readings have lowered slightly, although I know at home tests do have a level of error, and are all under 6 for FBS and under 7 for PPBS. My problem is that yesterday I decided to do a whole day of testing where I measured FBS and then PPBS after each meal, everything was fine until my after dinner reading. I had a particularly carb light meal and got a reading of 8.1. I thought that this must be a mistake and took another reading within seconds and got a result of 7.7. As this was higher than all my recent results including the ones taken earlier in the day I checked again and got 7.1 and then again and got 8.5. I didn't know why I got these results and left it there and thought I would check again the next day.

Today, I decided to check my lunch PPBS value and got 7.0 I then tested again within a minute and got 6.3. This confused me even further.

My question is, what could cause varying results like this? I know that at home tests aren't 100% accurate but I haven't had PPBS results over 7.0 for long time and am really worried about what this means. Could blood from different fingers cause differing results? Could my monitor of broken or my test strips contaminated?

Any thoughts, experience or advice on this issue is greatly appreciated and apologies for the long post.

 

[mo1905]

How long after eating are you taking the PPBS reading ? Ideally, this should be 2 hrs after earing. If you take reading earlier than this, you will get higher readings as your body is still dealing with the food. Even non-diabetics get peak readings shortly after eating. Also, what do you consider "a healthy diet" ? This can vary greatly and, for example, lots of fruit will give high readings. You shoul try to reduce carbs as well as sugars. Lastly, as you mentioned, the tolerances in the home glucose monitors can be up to 20% which is considerable.


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[wildrose]

Hello mo1905. Thanks for your response.

I take the test exactly 2 hours after I have finished eating and I have changed my diet to a Mediterranean one, with lots of fresh vegetables, lean protein and small amounts of complex carbs. For lunch today I had home made spicy beans, fist size amount sweet potato, half a cucumber, lots of broccoli and a few cherry tomatoes.

I understand that there is a level of error with the monitor but can't understand the variation in results within 5 minutes. Yesterday I had a swing of 7.1-8.5 in a matter of minutes.

I guess my real issue is I really want lower numbers and hate to see them go high!

 

[mo1905]

Your readings of 7.1 to 8.5 could actually have been 5.7 to 6.8 ( given 20% tolerance ). OK, maybe that is unlikely but you get my drift. Your diet seems fine and the numbers are a little high but there could be other factors playing a part too. Stress or illness can effect levels ( not saying you're ill lol ). How about exercise ? Regular exercise will certainly help.


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[wildrose]

I'm not ill, but the numbers have got me stressed.

I exercise everyday, brisk walk 2.5 miles, it usually takes around 30-35 minutes, 10-15 minutes of yoga in the morning.Recently, I have started running a few times a week although my pace is more of a jog. Planning to incorporate some strength training soon

I'm interested in how you calculated the 5.7-6.8. I thought a 20% level of error would put the 7.1 reading in a range of 7.24-6.96 (plus or minus 0.142). Have I got this completely wrong?

 

[mo1905]

7.1. 10% of 7.1 is 0.71. So 20% is 1.42.
7.1-1.42=5.68
Or, the other way is 7.1+1.42=8.52
So, a 7.1 reading can be anything from 5.7 to 8.5
Hope that makes sense.
The only way to reduce numbers further then would be try reducing carbs even further. The sweet potato is still fairly high, depending on how much you ate.


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[wildrose]

D'oh!

I can't believe I got 10% and 1% mixed up. Thanks for pointing it out.

I never really thought about the error before because I always had good numbers back. I guess monitors really are just an indicator.

 

[Brunneria]

Different fingers can sometimes give different readings.

And sometimes one batch of strips will read higher than another.

 

[Spiker]

You may have a specific reaction to one of the foods in that particular light carb meal. I would actually trust the meter reading, since you got a similar reading on a repeat test immediately after. In practice readings very rarely vary by +/- 20% on the same blood sample. If my meter did that I would literally throw it away. You did the right thing which is to repeat a test if you get an unexpected result. Don't act on a high result unless it is a consistent high result. Any result that can't be repeated or doesn't form a pattern should be ignored (except hypo levels).

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[wildrose]

Spiker - I think you are right. It seems that some carbs don't agree with me while I'm fine with others. At the moment I seem OK with complex carbs but as soon as I have something like noodles my blood sugar rockets.

I've stayed away from home testing for a while just because of the variation in readings. Seeing high numbers, or high for me, gets me worked up which probably raises my sugar levels further.

 

[Brunneria]

Wheat is the worst, for me. By a long way!
Other grains (rice, rye, barley...) are bad.
Potatoes and other root veg not so bad.

But everyone is different.

 

[Spiker]

I've stayed away from home testing for a while just because of the variation in readings. Seeing high numbers, or high for me, gets me worked up which probably raises my sugar levels further.

Please stick with the home testing and don't be discouraged. It's better to spot a high, and fix it, than never to have spotted it.

 

[wildrose]

Wheat is the worst, for me. By a long way!
Other grains (rice, rye, barley...) are bad.
Potatoes and other root veg not so bad.

But everyone is different.

Me too! Although I can get away with seedy bread.

 

[wildrose]

Please stick with the home testing and don't be discouraged. It's better to spot a high, and fix it, than never to have spotted it.

What about if you are pre-diabetic? Does it matter so much? I plan to have lab tests done every 3 months (FBS, PBS and HbA1c) to monitor my progress. Should I still monitor at home?

 

[Spiker]

What about if you are pre-diabetic? Does it matter so much? I plan to have lab tests done every 3 months (FBS, PBS and HbA1c) to monitor my progress. Should I still monitor at home?

If you are prediabetic the most important tests to continue are the 2 hour post prandial. This is like doing a little glucose challenge test every mealtime.

If you are happy with your current situation then going to tests every 3 months is probably fine.

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[runner2009]

Please stick with the home testing and don't be discouraged. It's better to spot a high, and fix it, than never to have spotted it.

I agree, with Spiker his advice is sound and it is good to try and identify foods that spike your BG and with a monitor you can do test on an individual food and get accurate results to see if you should eliminate that food

If you test for a couple of days and then plot your readings on a scatter gram graph, you will quickly see the outliers - the diabetic portion of mynetdiary has a preprogrammed one - and will put your mind to rest.


Sent from Runner2009 Burt