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Food, Health, and Eco-news
Is “Prediabetes” a Real Risk for the Real Thing?
Medicalization of moderately high blood sugar comes under scrutiny 05/02/2019 By Sherry Baker with Craig Weatherby

Diabetes is an enormous health problem in the US. In fact, it’s been called a national epidemic.

More than 30 million Americans have diabetes, and more than 95 percent have type 2 or “adult onset” diabetes — a metabolic disease driven by junky diets, excess weight, and sedentary lifestyles.

In addition, the U.S. Centers for Disease Control and Prevention (CDC) estimates that one in three Americans have a possible precursor condition, called prediabetes. 

Prediabetes is defined by blood sugar (glucose) levels that are abnormally high, but not high enough to qualify as diabetes. 

Such a blood sugar status is estimated to raise the risk that you’ll develop type 2 diabetes within five years, and the risks for type 2 diabetes, heart disease, and stroke.

Unsurprisingly, type 2 diabetes is usually preceded by prediabetes, and 15% to 30% of people with prediabetes will develop type 2 diabetes — unless they make diet and lifestyle changes that lower their blood sugar levels.

The American Diabetes Association (ADA) offers a diabetes risk test that's available as a download, or as an interactive online test that only takes about a minute to complete.

According to the ADA, doing two things will help people at risk prevent or delay the development of type 2 diabetes:

  • Lose 5% to 7% of your body weight (e.g., 10 to 14 pounds for a 200-pound person).
  • Get at least 150 minutes (2.5 hours) of physical activity, such as brisk walking, every week.

Nine out of 10 people with prediabetes don’t know they have this possible predictor of future diabetes, largely because most people don't have their blood sugar tested regularly.

But, since most people with prediabetes don't develop type 2 diabetes, and lifestyle measures can usually help control blood sugar, is it a condition that needs medical treatment?

There’s growing debate in the medical community about the answers to both questions — so we decided to scrutinize both sides of that divide.

Recent journalistic report deemed prediabetes a “dubious diagnosis”
Investigative science journalist Charles Piller recently outlined the ongoing controversy about prediabetes in the prestigious journal Science.

As he explained, the American Diabetes Association (ADA), and other diabetes organizations coined the term “prediabetes” out of concern about possible health dangers to patients with abnormally high blood sugar levels who didn’t meet the diagnostic criteria for diabetes (see “CDC and ADA say prediabetes requires action”, below).

“The fear was that prediabetes would lead to full-blown diabetes and thus there existed an opportunity to prevent the disease if prediabetes could be treated,” Piller writes.

Prediabetes was quickly and widely accepted as a strong indicator of future diabetes by the ADA, CDC, NIH and other health organizations.

But Piller questions whether higher than normal — but not in diabetes range — blood sugar levels should be deemed a separate medical condition.

He points to a lack of solid evidence that prediabetes causes health problems in people diagnosed with the condition. Likewise, he says there isn’t solid evidence that the higher-than-average blood sugar levels deemed a marker of prediabetes inevitably lead to full-blown diabetes.

What’s more, as Piller noted, treating prediabetes as a medical condition — which involves frequent blood-testing, extra doctor appointments, and possible therapy with blood-sugar lowering diabetic drug like metformin — can cause emotional and financial stress.

In addition, metformin can produce adverse side effects, including nausea, vomiting, stomach upset, diarrhea, weakness, chills, dizziness, constipation, heartburn, low blood levels of vitamin B-12, and/or a metallic taste in the mouth.

Credible critics question the meaning and risks of prediabetes
The World Health Organization (WHO) and some other international health associations have rejected prediabetes as a specific, meaningful diagnosis.

Like Charles Piller, diabetes expert John S. Yudkin, MD — an emeritus professor of medicine at Britain’s University College London — is dubious that prediabetes is a meaningful medical diagnosis.

Writing in the ADA’s Diabetes Care journal, Dr. Yudkin noted that while the concept of prediabetes relies on blood sugar levels alone, type 2 diabetes is a complex metabolic state that can’t be accurately captured by one measure.

Accordingly, Yudkin is critical of prescribing the blood-sugar-lowering drug metformin for prediabetes. He points to research showing that — when it comes to preventing or delaying full-blown type 2 diabetes — metformin is only about half as effective as lifestyle interventions such as weight control, exercise, and a healthy diet.

(To learn more about diabetes-deterring ways of eating, see our recent report, Top 5 Diets for Reducing Diabetes Risk.)

Moreover, metformin only appears to benefit people with prediabetes who have the very highest risk for progressing to type 2 diabetes, due to family history, obesity, and other risk factors.

Yudkin says the evidence doesn't support the idea that metformin or any similar drug will benefit all overweight people with higher than normal blood glucose levels — let alone everyone diagnosed with prediabetes.

Prediabetes didn't raise heart attack and other risks in heart patients
Studies in healthy people have found that heart attacks and sudden cardiac death are more common among people with prediabetes.

However, a recent study — the first of its kind — from Finland’s University of Oulu found that people diagnosed with coronary artery disease who also had prediabetes were not at higher risk for major adverse cardiac events.

Their six-year study involved 1, 948 people with existing coronary artery disease (CAD), including 417 met one of the key diagnostic criteria for prediabetes: impaired glucose tolerance or impaired fasting glucose.

And the results showed that the patients with prediabetes were not at increased risk of experiencing a major adverse cardiac event: a category that encompasses sudden cardiac death, heart failure, and acute coronary syndrome.

As the study’s lead author, Antti Kiviniemi, said, “We were able to demonstrate for the first time that prediabetes does not increase the risk of cardiac death and adverse cardiac events among patients with coronary artery disease.” (Antti M. Kiviniemi et al. 2019)

CDC and ADA say prediabetes requires action
The American Diabetes Association (ADA) says prediabetes “should not be viewed as a clinical entity in its own right but rather as an increased risk for diabetes and cardiovascular disease (CVD).”

That’s why the ADA’s medical and research chief William T. Cefalu, MD disagrees with the idea that prediabetes is a “dubious diagnosis.”

In his response to critics of the value of a prediabetes diagnosis, Dr. Cefalu emphasizes that even people at the lower end of the “too-high” blood sugar range still have a heightened risk for type 2 diabetes and for heart disease.

He believes that identifying and alerting people who meet the current criteria defining prediabetes is important because they will benefit from taking actions to improve and potentially protect their metabolic and heart health.

In response to Charles Piller's article, epidemiologist Lewis Kuller, PhD, of the University of Pittsburgh endorsed the prediabetes diagnosis to identify people at higher risk for type 2 diabetes, so that they can make appropriate lifestyle changes.

As Kuller noted, many people who meet the diagnostic criteria for prediabetes forgo these lifestyle changes, so he believes that more drastic approaches to lowering blood sugar in people with prediabetes — such as drugs or even bariatric surgery — must be considered.

What’s the bottom line?
It’s unwise to ignore higher than normal blood sugar, whether or not you’ve been given an official diagnosis of “prediabetes”.

And if you meet criteria for a diagnosis of prediabetes, it makes sense to lose excess pounds, develop a regular exercise program, and eat a healthy diet.

Those kinds of lifestyle changes alone may normalize your blood sugar levels and help you avoid type 2 diabetes while lowering your risk for heart disease.

Reminder: we recently reported on research into the best diabetes-prevention diets in Top 5 Diets for Reducing Diabetes Risk. You’ll find more relevant reports in the Metabolic Health section of our newsletter archive.


  • Antti M. Kiviniemi et al. Prediabetes and Risk for Cardiac Death Among Patients With Coronary Artery Disease: The ARTEMIS Study, Diabetes Care (2019). DOI: 10.2337/dc18-2549
  • Centers for Disease Control and Prevention (CDC). About Diabetes and Prediabetes. Accessed at
  • Centers for Disease Control and Prevention (CDC). New CDC report: More than 100 million Americans have diabetes or prediabetes. Accessed at
  • Classification and Diagnosis of Diabetes: Standards of Medical Care in Diabetes -2019. Diabetes Care 2019 Jan; 42(Supplement 1): S13-S28.
  • Kuller K. Letter to the Editor: Dubious Diagnosis, Bad Medicine. Science. April 2019.
  • Piller C. Dubious Diagnosis. Science. Mar 2019:
    Vol. 363, Issue 6431, pp. 1026-1031 DOI: 10.1126/science.363.6431.1026
  • Yudkin JS. Prediabetes: Are There Problems with This Label? Yes, the Label Creates Further Problems! Diabetes Care 2016 Aug; 39(8): 1468-1471. Accessed at