Prediabetes / Diabetes Screening Test
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What Are The Early Warning Signs of Prediabetes?

Medically reviewed by

Ford Brewer, M.D.


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Key takeaways

Over 30 million Americans are diabetic, a fact that has healthcare experts up in arms about this medical crisis in our midst. In the last 20 years, the number of adults diagnosed with diabetes has more than doubled

Less well-known, however, is the plight of the more than 88 million Americans who are prediabetic—most of whom are completely in the dark about their condition or the gathering risk it represents. 11% of prediabetics develop Type 2 diabetes within three years -- and that’s just the small minority of prediabetes cases that get diagnosed. These numbers could even be higher if numbers included those based on oral glucose tolerance tests were more widely used as a measurement. 

Prediabetes is clearly a risk factor for Type 2 diabetes, but it also distinguishes itself in being much easier to reverse. A diagnosis of prediabetes is an opportunity to reclaim health, quality of life, and potential lost years of life before the more serious condition manifests. 

What is prediabetes? What are the signs and symptoms? How can you catch it before it becomes full-blown diabetes?

What is diabetes?

Diabetes is a chronic condition that causes a patient’s blood sugar to be too high. Most of the food we eat gets converted to the simple sugar glucose, which enters the bloodstream and gets carried to every cell in the body to be used as fuel. A key component of this process is insulin, a hormone produced by the pancreas that allows the glucose to pass out of the blood vessels and into the destination cells.. 

However, diabetes impedes this process in one of two ways:

  • Type 1 diabetes - This autoimmune disease affects the pancreas - where the pancreas does not produce sufficient insulin, usually from childhood or adolescence. However, Type 1 diabetes can develop at any age. 
  • Type 2 diabetes - This condition is when the body develops a resistance to the effects of insulin, and cannot maintain appropriate blood sugar levels. This is often as a result of lifestyle factors like a poor diet or lack of exercise, and age plays a significant risk factor.

In either type, the glucose can’t leave the bloodstream, resulting in high blood glucose (or “blood sugar”) levels.There are several tests for diabetes including an average blood sugar test (A1C), fasting blood sugar, or glucose tolerance test can help diagnose diabetes. A blood glucose level under 120 milligrams per deciliter (mg/dL) is considered optimal for a glucose tolerance test. A blood glucose level of 200 mg/dL two hours after eating, or during a random blood sugar test indicates that the patient has diabetes.

Left unmanaged, high blood sugar can lead to a number of long-term and serious health consequences, including but not limited to stroke, heart attack, nerve damage, kidney problems, and eye problems. Long-term, these can lead to blindness, amputations, and death. People with Type I diabetes live 20 years less on average than non-diabetics; people with Type 2 diabetes live 10 years less on average than non-diabetics.

Diabetes can be managed with medication and lifestyle changes, but there is no cure for Type 1 diabetes. Some evidence indicates that Type 2 diabetes can be reversed, at least in some patients with decreasing body fat, increasing muscle mass, and decreasing high insulin values.

What does it mean to be prediabetic?

Prediabetes refers to a condition of elevated blood sugar that does not rise to the level of diabetes—that is, 200 mg/dL in the blood two hours after eating.

A person with blood sugar levels between 141 and 199 mg/dL after a glucose tolerance test is considered prediabetic. People who are prediabetic are at higher risk of progressing to Type 2 diabetes, as well as being at higher risk for stroke, heart disease, and other conditions.

Prediabetes distinguishes itself from Type 2 diabetes in that it is easier to reverse than Type 2 diabetes. However, many people are prediabetic and do not know it. Out of an estimated total of 88 million prediabetic persons over the age of 20 in the United States, 84% are unaware of their prediabetic status—in other words, unaware that they are at higher risk of developing a more serious chronic condition, and that they have a window of opportunity to reverse the condition. This number could be even higher if oral glucose tolerance tests were done more frequently to screen for prediabetes.  

For this reason, the unknown condition that could be lurking around any corner, it is worth keeping an eye out for the warning signs of prediabetes and getting tested if any of them manifest. Discovering prediabetes before it progresses to Type 2 diabetes can result in far fewer health consequences, higher quality of life, and longer life expectancy.

Warning signs of prediabetes

Prediabetes often goes undiagnosed, with the vast majority having no symptoms at all. However, certain symptoms may indicate that an individual is prediabetic. Many of these symptoms could indicate other conditions, but it may be worth checking for the condition as a measure to prevent the onset of Type 2 diabetes. Sadly, too many medical professionals don’t know enough about prediabetes and how to diagnose it properly, and it doesn’t help that the typical doctor visit is already too short. For prediabetes, it’s important to get to know the risk factors, symptoms, and to be tested if you’re at risk!

Keep in mind, you may not have all symptoms or any symptoms at all. Ford Brewer MD, MPH is a board-certified preventative medicine doctor who specialises in heart health and diabetes. 

Most patients don’t have warning signs

The vast majority of cases Dr. Brewer sees in his clinic have no symptoms, but are still prediabetic. This is one of the reasons why almost 90% of those with prediabetes don’t know they have it.

However, there are those who may notice the following symptoms and warning signs:  

1. Increased hunger

Glucose gets into the bloodstream because our digestive system breaks our food down into glucose, a simple sugar that our cells can easily use as fuel. In healthy individuals, this sugar passes from the bloodstream into the cells to fuel them.

If the glucose gets trapped in the bloodstream and never makes it to the cells due to lack of insulin or insulin resistance, the fuel never makes it inside the cells. Regardless of how recently the patient ate, the cells feel deprived of energy, as if the person was starving or fasting. As a result, the cells trigger the brain to crave more food.

Excessive hunger is a classic warning sign of prediabetes—a compulsive need to eat so the cells get the fuel the body needs. Unfortunately, if the sugar is unable to leave the bloodstream, excessive eating will cause the blood sugar to spike even higher, causing further problems and progressing toward Type 2 diabetes.

2. Frequent urination

When the body does not absorb glucose, the kidneys will try to absorb it as part of their job cleansing your blood. If the kidneys can’t keep up with the excess blood sugar, they will pass it into the bladder and try to get your body to excrete the glucose as urine. The glucose causes the bladder to fill up with fluid to excrete the sugar. 

As a result, the need to urinate more frequently than usual is a telltale warning sign of prediabetes. ‘Frequent urination’ is defined as the need to urinate seven or more times within 24 hours, having consumed two liters of water within that 24-hour time period.

This process is very taxing on the kidneys. Studies show that prediabetics often have the signs of chronic kidney disease, including excess protein in the kidneys and an inhibited estimated glomerular filtration rate (eGFR).

3. Increased thirst

One of the consequences of frequent urination due to prediabetes is that the body diverts water into urine in an attempt to flush out the excess sugar. This leaves the body with insufficient water to perform the many functions that water facilitates. As a result, dehydration sets in.

A warning sign of prediabetes may be excessive thirst in response to the lack of fluids. If you feel an excessive need to drink water or experience signs of dehydration frequently, it may be a sign that you are prediabetic. Drinking more water leads to more frequent urination, so these symptoms may go together or compound each other.

Prediabetic persons may exacerbate their condition if they attempt to quench their thirst with juice, soda, or other sugary beverages. These drinks can cause the blood sugar to spike even higher, taxing the kidneys even further and resulting in more urination without hydration to replace the lost fluids. Like frequent urination, this symptom is not that common in cases with prediabetes, and is often limited to extreme cases. 

4. Feeling tired all the time

Another warning sign of prediabetes is feeling tired all the time - although it might be hard to differentiate the type of tired that is part of the average aging process. If glucose is not making it into the cells due to lack of insulin or insulin resistance, the cells are not getting the fuel they need to function. This often results in a generalized sensation of fatigue. This fatigue may be accompanied by dizziness, headaches, irritability, trouble concentrating, trouble remembering things, muscle weakness, slow reflexes, and loss of motivation. 

High blood sugar can also cause inflammation, which the body interprets as a sign that it needs to rest and recuperate. This effect may add to the sensation of fatigue. 

Fatigue and apathy can be of particular concern, since the patient may not have the energy or attention needed to exercise, one of the key factors in reversing prediabetes. It can also lead to depression and the adoption of unhealthy eating habits, which cause insulin to be overproduced and contribute to the insulin resistance that characterizes Type 2 diabetes.

5. Tingling or numbness in your fingers or toes

High blood sugar can damage small nerves. This is known as “diabetic neuropathy,” but it can start to manifest even in prediabetic persons. The clearest sign of diabetic neuropathy is a tingling, burning, or numb sensation in the fingers and the toes. 

As the condition advances, diabetic neuropathy may lead to foot ulcers and charcot foot. Extreme cases may require amputation of the foot. 

Neuropathy, or numb or tingling fingers and toes are a warning sign of prediabetes, making them an opportunity to identify this condition before it gets worse and to undo the damage by taking steps to reverse the course of prediabetes before it worsens into Type 2 diabetes.

6. Blurred vision

High blood sugar also causes the eyes and the tissue around them to swell, the capillaries and small blood vessels in the eyes to rupture into microaneurysms. This distorts the shape of the lens in your eye, making it impossible or difficult for the eye to focus properly. 

The result is blurred vision, even in patients who wear glasses or use contact lenses. This effect is called ‘diabetic retinopathy’. Left unchecked, it can progress to detachment of the retina and ultimate blindness, especially in patients whose condition advances to Type 2 diabetes.

Diabetic retinopathy is a warning sign for prediabetes. It can be reversed if prediabetes is halted and the patient reestablishes a healthy baseline blood sugar.

Prediabetes risk factors

While there is no unified profile of a prediabetic, certain conditions lead to an increased risk of developing prediabetes. Risk factors for prediabetes include: 

Advanced age

Advancing age strongly correlates with insulin resistance, which leads to prediabetes and Type 2 diabetes which is prevalent in persons 45 years and older. A common phrase about diseases like diabetes is that “genetics loads the gun, but lifestyle pulls the trigger.” 

Evidence indicates that the body becomes naturally more insulin resistant with age, making older people more likely to develop prediabetes in the presence of other risk factors. Older people also tend to store excess fat, develop muscle mitochondrial syndrome, and suffer from inflammatory disorders, all of which contribute to insulin resistance.

The risk of prediabetes increases substantially in adults over the age of 45, and raises to almost 50% past the age of 65

Being overweight

People who are overweight or obese tend to have excess body fat. This excess body fat can lead to a number of serious health complications. Prediabetes is one such complication.

Fat cells tend to increase insulin resistance. If the condition advances far enough, Type 2 diabetes could be the end result. However, there will probably be an interim period—perhaps a quite long period—where the excess weight produces enough insulin to elevate the blood sugar, but not enough insulin to induce full-blown diabetes. This is the “prediabetic” period that could devolve into Type 2 diabetes if the excess weight is not managed.

Excess body weight or obesity is one of the most pervasive risk factors for prediabetes, as well as Type 2 diabetes. Doctors estimate the increased risk of Type 2 diabetes relative to excess weight as follows:

  • Overweight (BMI 25.0–29.9): 1.6x more likely
  • Class I Obesity (BMI 30.0–34.9): 3x more likely
  • Class 2 Obesity (BMI 35.0–39.9): 6x more likely
  • Class 2I Obesity (BMI 40.0+): 12x more likely

High blood pressure 

Elevated blood glucose causes the blood vessels carrying the sugary blood to lose their elasticity. Unable to stretch, the vessels constrict the flow of blood, causing the heart to work harder to pump it. This leads to high blood pressure. High blood pressure and Type 2 diabetes are common co-occuring conditions. This is true of prediabetes as well. 

Ranges of blood pressure are as follows:

  • Normal: 120 systolic / 80 diastolic
  • Elevated: 120–129 systolic / 80 diastolic
  • High Blood Pressure (Hypertension) Stage 1: 130–139 systolic / 80–89 diastolic
  • High Blood Pressure (Hypertension) Stage 2: 140 or higher systolic / 90 or higher diastolic
  • Hypertensive Crisis: 180 or higher systolic / 120 or higher diastolic

High blood pressure also shares a number of other risk factors with diabetes and prediabetes, including excess body weight, poor diet, sedentary lifestyle, lack of exercise, insufficient sleep, Vitamin D deficiency, smoking tobacco, and advancing age. 

High blood pressure combined with high blood sugar can increase the risk of stroke, heart attack, kidney disease, ocular blood vessel ruptures leading to vision loss, and peripheral vascular disease. 

Family history

A family history of diabetes is a significant risk factor in the development of prediabetes. A study of 8,000 subjects showed that patients with diabetes in their family were 26% more likely to be prediabetic. It’s important to note that family history was important even in non-obese individuals. 

Being sedentary

Lack of exercise is strongly correlated with excess body weight and poor diet, both of which contribute to high blood sugar and insulin resistance. 

The impact of a sedentary lifestyle on susceptibility to prediabetes goes further, however. Lack of exercise causes the muscle cells themselves to become resistant to insulin. Regular movement is imperative. 

Even a person who has enjoyed an active lifestyle for a long period of time may be at increased risk if they cease their exercise regimen, whether due to injury, lifestyle change, or falling off the habit. A study by University of Missouri Institute for Clinical and Translational Sciences revealed that people who reduced the intensity of their exercise regimens by half exhibited an increased lack of glycemic control (blood sugar regulation). Even a few days off of regular movement shows a change, so keep moving! 

High cholesterol or high triglycerides 

Triglycerides are a type of fat particle that is found in the blood; HDL and LDL cholesterol are waxy substances found in the blood created by the liver and added to by the foods you eat. High triglycerides or cholesterol are not causes or symptoms of diabetes or prediabetes in and of themselves. However, they are linked to an inability of the body to properly use food. Insulin doesn’t just help the body absorb glucose; it also stops the body from burning fat and puts the fat into storage. 

Too much fatty particles in the blood has its own health implications, including an increased risk of heart disease and stroke. This is not the same thing as being diabetic or prediabetic. However, high triglycerides may be an indication that the body is becoming resistant to insulin, which may mean that the blood sugar is spiking along with the triglycerides and cholesterol.

High triglyceride and cholesterol levels in the blood are also associated with other prediabetes risk factors, like excess weight, obesity, lack of exercise, aging, and high blood pressure.

Healthy triglyceride levels break down as follows:

  • Normal: 150 mg/dL or lower
  • Borderline: 150–199 mg/dL
  • High: 200–499 mg/dL
  • Very High: 500 mg/dL or higher

While optimal cholesterol levels found in HDL, LDL, total cholesterol and other types of cholesterol are often used for the purpose of gauging heart disease risk, further advanced cholesterol testing may be necessary based on your risk factors. 

Another great and simple measurement that is found right in your cholesterol panel is Triglycerides over HDL-C. However, it should not be relied upon alone, much like other tests, to determine the health of glucose metabolism. 

Sleep apnea 

Sleep hygiene is incredibly important for overall health. Poor sleep has many health effects. 

One of these sleeping issues, obstructive sleep apnea (OSA) causes interruptions in breathing during the sleep cycle. Often associated with loud snoring, sleep apnea can cause fatal respiratory arrest without treatment. 

OSA may be associated with glucose intolerance and insulin resistance. OSA also correlates with excessive body weight, another risk factor for prediabetes. Doctors think that overweight or obese people may be more susceptible to sleep apnea because of fatty deposits around the airway. 

How to reverse prediabetes

A diagnosis of prediabetes may be unpleasant, but it’s also a golden opportunity to correct course before the condition worsens into Type 2 diabetes, which carries many detrimental health consequences and is much harder to reverse. 

Actions a patient can take to reverse prediabetes and prevent the development of Type 2 diabetes include:

Dr. Brewer’s number one tip

To get yourself down to a healthy level of body fat. Overweight persons can significantly reduce their risk of developing Type 2 diabetes by losing as little as 5-7% of their body weight. For a person weighing 200 pounds, that’s just 10-14 pounds.

Other opportunities that can help reduce body fat, and help prevent T2D include:

  • Healthy eating - Reduce caloric and fat intake if too high, and focus on eating fiber, whole foods, fruits, and vegetables. While whole grains are typically recommended over refined grains - all grains can have a high glycemic index and cause elevated blood sugar. This needs to be considered for anyone with an issue metabolizing sugars. 
  • Exercise - Try for 75 minutes of vigorous aerobic exercise, or 150 minutes of moderate aerobic exercise, every week. Build up to longer workouts when you are ready. Dr. Ford Brewer stresses the importance of building muscle mass for everyone, especially for those over 65 to help stabilize glucose. 
  • Quit smoking - Smoking increases the risk of developing Type 2 diabetes.
  • Consider medications - Medications like metformin can help manage prediabetes. Medications to manage high blood pressure and cholesterol levels may also be appropriate. However, Dr. Brewer stresses “you can’t out supplement lifestyle.” Medications and supplements can help, but healthy lifestyle habits should be the primary goal. 

For more help, read our guide to 13 ways to reverse prediabetes.

When to test for prediabetes 

Anyone exhibiting the warning signs of prediabetes, with a family history of diabetes, or have any of the risk factors for prediabetes should have their fasting blood levels tested. Imaware currently provides a home diabetes/prediabetes test to measure your HbA1c glucose levels which is a key indicator of the disease.

Another test, recommended by Dr Brewer to use in combination, is an oral glucose tolerance test, typically used to diagnose gestational diabetes during pregnancy. However, this test is now being used to assess glucose regulation in those with prediabetes. This test consists of three glucose readings - a fasting level, one hour aftering drinking a sugary drink, and two hours after the sugary drink. Dr Brewer recommends the oral glucose tolerance test yearly after the age of 65 to prevent the transition from prediabetes to Type 2 Diabetes. 


Remember, the vast majority of cases of prediabetes are asymptomatic which is why the majority of those with prediabetes don’t know they have it. Any symptoms of prediabetes are often mistaken for symptoms of other conditions, and may very well be linked to other conditions. 

However, prediabetes symptoms should not be dismissed without testing. Moreover, discovering prediabetes is a crucial opportunity to prevent the condition from progressing to Type 2 diabetes as prediabetes is reversible with lifestyle changes.

Warning signs of prediabetes might include:

  • Increased hunger
  • Frequent urination
  • Dehydration or constant thirst. 
  • Fatigue
  • Blurred Vision
  • Numb or tingling fingers and/or toes

People who are at increased risk of prediabetes should also consider getting tested. This includes people who:

  • Are overweight or obese
  • Have high blood pressure
  • Are 45 years of age or older, especially 65 years of age or older
  • Have a family history of diabetes or prediabetes
  • Don’t exercise or recently reduced physical activity
  • Have high triglycerides and/or high cholesterol
  • Have obstructive sleep apnea
Updated on
September 13, 2021
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