New Research on High Glucose Levels

American Diabetes Association (ADA) guidelines advise “lowering A1C[1] to below or around 7%” and postprandial (after-meal) glucose levels to 180 mg/dl or below. But new research shows that these glucose levels damage blood vessels, nerves, organs, and beta cells.

An article by diabetes blogger Jenny Ruhl analyzes at what blood glucose level[2] organ damage starts. According to Ruhl, research shows that glucose can do harm at much lower levels than doctors had thought.

This news could be discouraging or even terrifying. If it’s hard to meet your current glucose goals, how will you reach tighter goals? Such news might make some people give up. But remember, a high postprandial or fasting reading won’t kill you. All we know is that higher numbers correlate with higher chances of complications. You have time to react.

In fact, we could choose to look at this as good news. We all know of people who developed complications despite “good control.” But complications are not inevitable; it’s just that so-called “good control” wasn’t really all that good.

First, the numbers. “Post-meal blood sugars of 140 mg/dl [milligrams per deciliter] and higher, and fasting blood sugars over 100 mg/dl [can] cause permanent organ damage and cause diabetes to progress,” Ruhl writes.

For nerve damage, University of Utah researchers studied people[3] with painful sensory neuropathy, or nerve damage. They found that participants who did not have diabetes but who had impaired glucose tolerance on an oral glucose tolerance test, or OGTT, (meaning that their glucose levels rose to between 140 mg/dl and 200 mg/dl in response to drinking a glucose-rich drink) were much more likely to have a diabetic form of neuropathy than those with lower blood glucose levels.

The higher these OGTT numbers go, the more nerve damage is found[4], according to Johns Hopkins Hospital researchers. The OGTT gives a good idea of how high after-meal blood glucose levels are likely to be.

Glucose can also start killing beta cells at levels below 140. One study found that people with fasting blood glucose from 110–125 (within the official “prediabetic” range) had already lost[5] up to 40% of their beta cell mass.

Italian researchers found that even with glucose levels in the supposedly “normal” range, beta cells started to fail[6]. Ruhl says that researchers “found that with every small increase in the 2-hour glucose tolerance test result, there was a corresponding increase in…beta cell failure. The higher a person’s blood sugar rose within ‘normal’ range, the more beta cells were failing.”

Failing beta cells will lead to worsening diabetes, a truly vicious cycle. Slightly elevated glucose has also been shown to cause eye damage (“retinopathy”) and increased rates of heart disease, kidney damage, and stroke.

Where Does High Start?
Studies like the ones Ruhl quotes and others indicate that damage occurs with even slightly elevated blood glucose. But what can you do about that? Is it reasonable to try to keep glucose at normal levels all the time?

It seems for some people, that course would lead to frustration and burnout. In fact, ADA says that older, sicker people should have even less strict goals. How do you set reasonable goals for yourself?

Keeping normal numbers may require extraordinary effort. It may require very low carbohydrate intake. It may not be possible for you. If you’re taking insulin or drugs in the sulfonylurea or meglitinide classes, aiming too low can put you at risk of hypoglycemia[7] (low blood glucose). The whole thing can make you crazy, because sometimes numbers will go up for no apparent reason.

As a result, most people set less-demanding goals for themselves. If they can keep their postprandial glucose under 180 and their fasting below 120, they’re OK, and the ADA agrees.

There’s nothing wrong with that. People can trade off how low they want their blood glucose against how much work they are willing to do and how many foods they’re willing to cut back or give up. They are adding to their risk, but, to me, quality of life is the most important thing.

Important note: Bringing blood glucose down by means of multiple drugs has NOT been shown to decrease complications much. Two huge studies, the ACCORD[8] and ADVANCE trials[9] showed this.

But people who manage to keep normal or near-normal numbers through healthy eating and living and intelligent use of medicines seem to live long, relatively healthy lives. They can even reverse type 2[10] or the complications of Type 1, even if they have spent years with elevated blood glucose before getting them under control. It’s almost never too late to get on track.

So my question is what are your target numbers? How high is too high for you? Does it make sense to aim for normal, non-diabetic levels, or is that just too demanding and unrealistic? If you had a newly diagnosed friend or relative, what would you tell him or her about glucose goals?

Want to learn more about blood glucose numbers? Read “What Is a Normal Blood Sugar Level?”[11] and see our Blood Sugar Chart.[12]

  1. “lowering A1C:
  2. what blood glucose level:
  3. studied people:
  4. nerve damage is found:
  5. already lost:
  6. started to fail:
  7. hypoglycemia:
  8. the ACCORD:
  9. ADVANCE trials:
  10. reverse type 2:
  11. “What Is a Normal Blood Sugar Level?”:
  12. Blood Sugar Chart.:

Source URL:

David Spero: David Spero has been a nurse for 40 years and has lived with multiple sclerosis for 30 years. He is the author of four books: The Art of Getting Well: Maximizing Health When You Have a Chronic Illness (Hunter House 2002), Diabetes: Sugar-coated Crisis — Who Gets It, Who Profits, and How to Stop It (New Society 2006, Diabetes Heroes (Jim Healthy 2014), and The Inn by the Healing Path: Stories on the road to wellness (Smashwords 2015.) He writes for Diabetes Self-Management and Pain-Free Living (formerly Arthritis Self-Management) magazines. His website is His blog is

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