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The Trouble with Glucose Testing

A big new review shows that people who don’t use insulin are wasting their time and money when they test their blood glucose.

I agree.

And I still recommend that everyone who has diabetes test his or her blood.

Do I contradict myself? I don’t think so.

The new review comes from the Cochrane Collaboration, the most respected group that reviews scientific studies. Six European experts reviewed a dozen randomized controlled trials of 3259 people with diabetes. The review, “Self-monitoring of blood glucose in patients with type 2 diabetes mellitus who are not using insulin,” just appeared in the Cochrane Library.

The main conclusion of the study is that, “Glycaemic control in patients with type 2 diabetes who are not using insulin is small up to six months after initiation and subsides after 12 months.” I’m surprised that it has even a small effect.

Actually, blood glucose testing doesn’t have any effect on our levels. Testing is a tool that we have to learn how to use. And few of us are lucky enough to have a doctor or nurse who will take the time to show us what to do.

What we do after we test makes all the difference. The usual pattern is to do nothing, so we get nothing.

When we do follow up on our blood glucose tests, we often do it at the wrong time. For example, a friend told me over lunch this week that she tests her blood glucose. She always tests it the first thing in the morning, and it’s always high, but she doesn’t know what to do about it.

The problem with checking our fasting level is that short of a total lifestyle makeover or gene transplant we can do little about it. High fasting blood glucose comes from the dawn phenomenon that comes in part from what we at the previous day and in part from the body’s natural glucose boost to prepare for the day ahead.

Most of us, however, probably check our level two hours after the first bite of a meal. This is the standard recommendation, and it makes sense.

But we could check one hour after the first bite or 72 or 74 minutes afterwards, which studies show is when our level typically reaches a peak. I don’t think it matters much how long after eating we wait to test as long as we are consistent.

But then what? Knowledge of our levels can give us power over managing them, but only if we do something. That something is the activity most lacking.

Our medical professionals generally don’t tell us what we can do. But we can do something right away to manage our levels immediately. And we can do something else to manage our levels after our subsequent meals.

But first we have to know what level is too high. And that depends on who you ask. The American Diabetes Association has the most lax standards, saying that our level two hours after a meal should be no more than 180 mg/dl. Dr. Richard K. Bernstein, the guru of low-carb eating, says that your level shouldn’t rise at all after meals. You decide what your current standard is, recognizing that as your control gets better you may set a higher standard.

We have to know why we want our level to be normal. It’s because the higher our blood glucose levels the greater our risk of serious complications down the road.

Then, if your level is too high by your standard, one thing that you can do to immediately bring it back to normal is to get some vigorous exercise. Actually, it doesn’t take much exercise, as I well remember when my late wife’s blood glucose level was about 250 mg/dl after dinner one night. What to do? she wondered. Go for a walk, I suggested. When we returned in less than half an hour after a leisurely stroll, her level had dropped considerably.

Long term management of our levels is just as easy, as long as we understand how different foods affect us. The key is that diabetes is simply a disease where we can’t handle carbohydrates like most people can. Carbohydrates have an outsize effect on our blood glucose levels. Protein will have a small effect, and fat has none.

As a result, it’s only when we eat lots of carbs that our levels shoot up. The worst culprits are the grains and other starches, like potatoes.

But don’t take my word for it. See for yourself how different foods increase your blood glucose levels. And then take the next step after testing. That next step is making a change.

This article is based on an earlier version of my article published by HealthCentral.

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  • Dan Karkoulas at

    Thanks for your response. You are a great resource for diabetics and their families (my wife is diabetic.) Should low-carbing diabetics eat at least a small amount of carbs at each meal to cover even the lower quantity of insulin?

    • David Mendosa at

      Dear Dan,

      To the best of my knowledge, neither I nor anyone who advocates a very low-carb diet recommends eating NO carbs. For example, Dr. Bernstein recommends up to 6 grams for breakfast and 12 grams each for lunch and dinner.



  • Dan Karkoulas at

    Should a person who gets a reading of 14(Canada) 2 hours after eating take more insulin at that time?

    • David Mendosa at

      Dear Dan,

      Please don’t trust any answer you get on the Internet to this question. This is the sort of question that you need to discuss with your doctor.



  • Craig at

    Nice article- particularly the “what you can do NOW” aspect of it. As a newly diagnosed T2, I’m aggressively managing lifestyle. I liken it to going from driving a reliable Honda to a British sports car. The Brit can go faster, look better, and be way more fun… but you are ALWAYS working on it and tweaking it, just to keep it going. Just call me Aston Martin.

  • Diana at

    Thanks for such a great article. It’s a shame that we aren’t taught how to use these tools to our advantage. I think this article will help a lot of other T2s.