Prediabetes symptoms: Recognise the signs and reduce your risk

What are the symptoms of prediabetes? Read on for signs and risk factors, as well as lifestyle changes that may reduce your risk.
Published 15 September 2022 | Updated 28 May 2024

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Talk about a sneaky symptom: You can’t see or feel your blood sugar level, but it’s one of the most important indicators of your long-term health. Chronic high blood sugar increases your risk of heart disease, stroke, nerve and eye problems, kidney disease—and of course, diabetes. Most people know that type 2 diabetes (T2D) is an epidemic around the world. But more than two million Australians have prediabetes and are at high risk of developing type 2 diabetes according to Diabetes Australia.

While prediabetes can be managed or even reversed with lifestyle changes, it often goes untreated because 84% of people don't know they have it. And that knowledge gap can greatly affect a person’s future health: Without treatment, up to 30% of people with prediabetes will develop T2D within 5 years.

Could you—or someone close to you—be at risk? Here are the signs, risk factors, and preventive measures you need to know.

What is prediabetes (borderline diabetes)?

Prediabetes (also referred to as borderline diabetes) is diagnosed by measuring blood sugar (or “glucose”) levels, but it’s really about insulin. Insulin is a hormone produced in the pancreas that helps cells take glucose from your bloodstream for energy. When you have prediabetes, your cells have trouble using insulin, which causes glucose to build up in the blood. As time goes on, this insulin resistance can prompt the pancreas to produce less insulin, which causes blood sugar levels to climb even higher. The result is type 2 diabetes—and all the health complications that come with it. On the other hand type 1 diabetes is an autoimmune disease and is caused by damage to the pancreas, reducing its ability to produce insulin.

When you’re at the borderline level of diabetes, you’re not necessarily immune to the disease’s negative health effects. “While blood glucose levels may not yet be high enough for a diagnosis of T2D, they are still elevated which can lead to the same complications,” says Melissa Joy Dobbins, M.S., RDN, a registered dietitian and certified diabetes educator. That’s because if too much glucose stays in the bloodstream it becomes toxic to tissues and organs. “Over time, that can damage the heart, nerves, eyes, kidneys, and more,” Dobbins says. “So these complications can have a very significant impact on a person’s health and quality of life.”

While people with prediabetes may have some symptoms, often there are no obvious signs. “A blood test is the only way to know if you have it,” says Jill Weisenberger, M.S., RDN, a registered dietitian and certified diabetes educator. There are two basic kinds your doctor may order:

  • Fasting plasma glucose (or FPG) Often run as part of routine blood work, an FPG provides a basic snapshot of your blood sugar level before you’ve had anything to eat.

How to read a fasting plasma glucose test:

Less than 100mg/dl


100 mg/dl – 125 mg/dl


126 mg/dl or higher


  • HbA1c (or A1c) If your doctor already suspects you have prediabetes or diabetes, you might get this test, which provides a 2- to 3-month average of your blood sugar levels.

How to read an HbA1c (or A1c) blood glucose test:

Less than 5.7%


5.7% - 6.5%


6.5% or higher


Causes and risk factors of prediabetes

Are you likely to develop prediabetes? The causes may surprise you. While obesity and a sedentary lifestyle make you more prone to insulin resistance, there are many other things that can affect your risk. “Plenty of lean, active people with balanced diets still get prediabetes and type 2 diabetes,” Weisenberger says.

Research shows that the following factors increase your risk of prediabetes:

  • Diabetes runs in your family. Experts aren’t sure if this is because lifestyle habits like diet and physical activity tend to be similar in families, but whatever the reason: If close relatives have diabetes, you’re more likely to get prediabetes.
  • Weight gain. Carrying extra kilos causes hormonal changes that interfere with your body’s ability to use insulin. And since people tend to gain weight as they age, this may help explain why people over 45 also have a higher risk of developing prediabetes.
  • Activity levels. Muscles need lots of energy to move, so they use more glucose from the bloodstream during exercise. A lack of physical activity makes your body more prone to high blood sugar levels.
  • Diet. Muffins, biscuits, and cake all rapidly increase your blood sugar levels—and they have another unfortunate effect too. When you fill-up on foods low in vitamins and minerals, you typically don’t eat enough nutrient-rich foods. This can prevent your body from getting what it needs to protect itself from diseases like diabetes.
  • Having gestational diabetes. Women who have high blood sugar levels while pregnant have a 35 to 60% likelihood of developing type 2 diabetes within 5 to 10 years of pregnancy. “If you had even a borderline response, much less a positive response, to a glucose tolerance test while pregnant, you have a higher risk of diabetes now and later,” says Florence Comite, MD, and endocrinologist.
  • Having polycystic ovarian syndrome (PCOS). An estimated 65 to 70% of women with this hormonal disorder have insulin resistance, which causes high blood sugar levels. More than half of people who have PCOS will develop type 2 diabetes by the age of 40.
  • Race. Aboriginal and Torres Strait Islander people are almost four times more likely than non-Indigenous Australians to have diabetes or prediabetes. Also being African American, American Indian, Pacific Islander, or Hispanic/Latino can increase someone's risk. Although there’s no definitive reason why people of some races and ethnicities are more likely to develop prediabetes.

Signs and symptoms of prediabetes

Diabetes may come with hard-to-miss symptoms like blurred vision, but the signs of prediabetes are often subtle, making them easy to miss or mistake for other diseases. This may result in a lost opportunity to take action. Recognising this condition’s stealth symptoms can nudge you to make preventive lifestyle changes before it escalates.

Do any of these warning signs of prediabetes sound familiar? Make an appointment with your doctor for a blood test.

  • Thirst. “When blood glucose levels are elevated, the body works to get rid of excess glucose by flushing it out in the urine,” Dobbins says. That can result in a cycle of dehydration and thirst.
  • Exhaustion. It’s easy to write off fatigue as the result of poor sleep, but if you’re getting ample shuteye and still feel beat, high blood glucose levels might be to blame.
  • Light-headedness. Too much insulin can sometimes make you feel jittery or faint. “This is a sign of reactive hypoglycaemia, and for some people it’s a very early indicator of prediabetes,” Comite says.
  • Tingling pain in hands or feet. People with diabetes often complain of burning or discomfort in their extremities, and a small study found that people with prediabetes may experience this symptom, too. The culprit, high blood sugar levels, which damage small nerve fibres, causing pain.
  • Signs of heart disease. “Often people with type 2 diabetes or prediabetes also have high blood pressure, abnormal cholesterol levels, high triglyceride levels, or fatty liver disease,” Weisenberger says.
  • Don’t bounce back from a cold. Nerve damage from elevated blood sugar doesn’t just cause pain—it can slow circulation too, robbing the body of the nutrients it needs to heal.

5 ways prediabetes can be treated

If you have high blood sugar, some small lifestyle changes can make a big difference in preventing or delaying the onset of type 2 diabetes. What’s more, they may even reverse prediabetes. According to the American Diabetes Association, research shows you can lower your risk of developing type 2 diabetes by up to 58% by making changes like these:

1. Lose weight

Losing 5 to 7% of your body weight (4 to 6 kilos for a 85 kg person) can prevent or delay the onset of diabetes according to the American National Institute of Diabetes and Digestive and Kidney Diseases. For people with prediabetes, WeightWatchers® may be especially effective for weight loss. In one study, volunteers with prediabetes followed either WW or the American National Diabetes Education Program (NDEB). After one year, the people on WW lost 5.5% of their body weight while those following the NDEB lost less than 1%. The WW group also significantly improved their blood sugar and HDL cholesterol levels.

2. Get moving

“Being active encourages muscles to better utilise glucose for energy, and makes them more sensitive to insulin,” Dobbins says. One study found that a single moderate- to high-intensity workout improved a prediabetic person’s ability to use insulin by 51 to 85% for up to 3 hours. Physical activity also helps improve circulation, boosts heart and lung health, and can aid in weight loss. Diabetes experts recommend at least 30 minutes of moderate movement, like brisk walking, 5 times a week.

3. Rethink your eating patterns

The latest research reveals the foods you do—and don’t—eat affect how likely you are to have high blood sugar. “Diets high in red meats and sugar-sweetened beverages are associated with a greater risk of type 2 diabetes,” Weisenberger says. On the flip side, eating more nuts, berries, and yoghurt—and drinking coffee and tea—may lower your risk.

4. Stop smoking

Cigarettes contain toxic substances that injure cells throughout the body, preventing them from functioning properly. Smoking may also encourage the body to store belly fat, which increases levels of cortisol, a hormone that raises blood sugar levels.

5. Consider medication

Lifestyle changes are the most effective prediabetes treatment, but if they don’t significantly lower your fasting glucose or HbA1c levels, your doctor may recommend medication. Several studies have shown that the drug Metformin can help prevent prediabetes from progressing to type 2 diabetes.

The upshot: Am I prediabetic?

If you’ve noticed symptoms like thirst and fatigue—or have risk factors like a family history or gestational diabetes—you may be wondering “am I prediabetic?” The only way to know for sure is to get tested. If the results point to a diagnosis of prediabetes, don’t panic. You have more control over this condition than you might think! “Making positive health changes may tamp down blood sugar levels and insulin resistance, preventing or delaying the onset of type 2 diabetes,” Weisenberger says. But don’t wait, she adds: ”Your greatest opportunity for reversal is today.”