What Is Prediabetes: Symptoms, Causes, Diagnosis, And Treatment

Many people know about diabetes, a metabolic disease. Diabetes impairs your body's ability to process blood sugar, causing high blood glucose levels. However, many people may not be familiar with another related condition known as prediabetes.

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What is prediabetes?

Prediabetes, also known as borderline diabetes, is a condition where your blood sugar or blood glucose levels are slightly elevated but not high enough for a type 2 diabetes diagnosis. However, if left untreated, it can progress to type 2 diabetes. Prediabetes can cause other serious health problems such as stroke and heart disease. 

Fortunately, prediabetes is reversible. Medical intervention and positive lifestyle changes such as physical activity and healthy eating can bring your blood sugar levels back to normal.

Symptoms of borderline diabetes

Prediabetes often won't present any signs or symptoms. However, some people may experience acanthosis nigricans.¹ This condition indicates insulin resistance and has links to polycystic ovarian syndrome (PCOS). The condition does not arise in all cases of PCOS. When it does, the patient develops darkened, thickened skin on different body parts, including the knees, elbows, armpits, neck, and knuckles

However, some signs and symptoms could mean that prediabetes has progressed to type 2 diabetes. If you experience the following symptoms, you should talk to your doctor, who can order several tests to confirm the diagnosis.

  • Fatigue

  • Frequent infections

  • Increased thirst

  • Blurred vision

  • Slow-healing sores

  • Increased hunger

  • Frequent urination

  • Unanticipated weight loss

  • Tingling or numbness in the hands or feet 

What causes prediabetes?

The exact cause of prediabetes is unknown. However, genetics and a family history of the condition seem to be big risk factors. 

People with prediabetes don't process glucose properly. The largest amount of sugar in the body comes from your food. When digestion takes place, sugar moves into the bloodstream, and your body absorbs it into its cells for energy. Your pancreas produces insulin to aid this process, lowering blood sugar levels. 

However, if you have prediabetes, your cells don't respond to insulin as they should. They take in less sugar, causing sugar to accumulate in the bloodstream instead of fueling the cells. 

Here's how the prediabetes cycle happens:

  1. Your cells become insulin resistant and have a low or sluggish response to insulin. They don't let in the required amounts of sugar, so it stays in your blood.

  2. Your pancreas tries to get the cells to respond, secreting more insulin.

  3. The insulin makes up for the weak cells' response and brings your blood glucose levels back to normal for a while.

  4. However, your pancreas cannot maintain high insulin production, so your cells go back to absorbing little sugar. The unabsorbed sugar remains in your bloodstream. 

  5. Consequently, your blood sugar levels keep rising, and a blood test will show prediabetes.

  6. If left unmanaged, prediabetes may progress to type 2 diabetes.

Risk factors of prediabetes  

Certain factors increase your chances of developing prediabetes. These risk factors include:


Cells become more resistant to insulin if you have more fatty tissue, especially inside and between the muscle and skin around the abdomen (visceral fat). Therefore, being overweight is a risk factor for prediabetes. Doctors may test you for prediabetes if your body mass index (BMI) exceeds 25. 


Consuming red meat, processed meat, and drinking sugar-sweetened beverages can put you at a higher risk of developing prediabetes. 


Regular physical activity can maintain a moderate weight and reduce the risk of developing prediabetes. Therefore, less active people may be at a higher risk of developing the condition.


The risk of developing prediabetes is higher after age 45.

Family history

If you have an immediate relative such as a sibling or parent with type 2 diabetes, you're more likely to develop prediabetes.

Waist size

A large waist can increase the risk of developing prediabetes. This risk factor increases for women whose waist is more than 35 inches and men with a waist larger than 40 inches.  

Smoking tobacco 

If you smoke, you might be at higher risk of developing insulin resistance and ultimately prediabetes. There is a link between smoking and increased waist size, another risk factor. 

Medical history

Certain medical conditions might increase your risk of developing insulin resistance. These conditions include: 

  • Increased cholesterol or triglyceride levels

  • Gestational diabetes: Diabetes during pregnancy

  • Sleep apnea: A condition that interrupts sleep repeatedly

  • Polycystic ovary syndrome (PCOS): A hormonal condition causing irregular menstruation

Tests and diagnosis of prediabetes  

Doctors order blood sugar tests to diagnose prediabetes. The tests include:

A1C test

The A1C test is also known as hemoglobin A1c, HbA1c, or glycosylated hemoglobin. This test measures the average percentage of sugar attached to the hemoglobin in the last 2-3 months. If you have a high A1C, your average blood glucose levels have been high during that period. 

The normal A1C value is less than 5.7%. If the tests reveal an A1C of 5.7-6.4%, that may suggest prediabetes. If the A1C value is 6.5% and above, that points to type 2 diabetes. However, your doctor has to perform the test again on a different day to confirm the diagnosis. 

Fasting plasma glucose (FPG) test

The fasting plasma glucose (FPG) test measures the glucose in your blood after fasting overnight. An ideal fasting glucose test result is below 99 mg/dL, while the prediabetic range in this test is between 100 and 125 mg/dL. If the test result is above 125 mg/dL, that is an indicator of type 2 diabetes. Again, your doctor must perform the test on another day to confirm this diagnosis.

Oral glucose tolerance test (OGTT)

The oral glucose tolerance test (OGTT) measures your blood sugar after fasting overnight and again two hours after you drink a sugary liquid during the test. Normal blood sugar goes below 140 mg/dL within two hours, while the pre-diabetic range is 140-199 mg/dL. 200 mg/dL or more suggests type 2 diabetes.

What are the complications of prediabetes? 

Prediabetes can lead to type 2 diabetes if left unmanaged. It can cause other conditions, including:

How is prediabetes treated?

Lifestyle changes

If you are diagnosed with prediabetes, you can make some lifestyle changes to reverse the condition, including:

Regular physical activity

Regular exercise has great benefits as it lowers your blood glucose levels by moving sugar into your cells, where they use it as energy. Exercising also increases your body's sensitivity to insulin. This means your body won’t need to secrete lots of insulin to move glucose from the blood. 

If it's been a while since you went to the gym, start with a walk in the morning or evening to slowly reintroduce yourself to physical activity. You can begin by walking around the block and slightly increase the distance you walk every day. 

Choosing activities that you used to enjoy can make exercise far more exciting. For example, if you previously liked bike riding, resume the hobby. You can also try interesting activities like swimming and salsa. Chances are you'll stick with a workout you enjoy. 

You can also speak to your doctor to develop the right physical activity routine for you. 

Eating a balanced diet

Watching what you eat and switching to healthier options is another way to manage prediabetes. Limit your intake of refined carbohydrates such as pasta and white bread, saturated fats, and sugary foods. 

Instead, eat many fruits and vegetables, lean proteins such as fish, whole grains, and low-fat dairy. These foods contain vitamins and minerals and are lower in fat.

Although most available research on diet focuses on type 2 diabetes rather than prediabetes, it would make sense for a person with prediabetes to consider a low carbohydrate diet. 

A low carbohydrate diet restricts carbohydrate intake to about 140g per day, less than 26%² of total daily calories. However, this approach may not be appropriate for people with conditions such as heart disease. It might take time to adapt to your diet change, even if it is only a small adjustment. Talk to your doctor before making major dietary changes.

Losing weight

Losing weight can lower the body's resistance to insulin, ensuring the body uses the hormone as it should. One study suggests that people with prediabetes could reduce the risk of type 2 diabetes by 16%³ for every 2.2lbs of weight lost. Increasing your water intake and avoiding sugar and simple carbohydrates are among the healthiest ways to lose weight. Exercising regularly is also a great way to burn more calories. 


Your doctor may prescribe medication to reverse prediabetes and prevent it from progressing to type 2 diabetes. Some drugs stimulate the pancreas to release more insulin, while others inhibit the release of sugar from the liver so that the body will need less insulin. Metformin is among the most common medications used to regulate blood sugar in the body.

SGLT2 inhibitors are a new class of oral medications that are increasingly popular in treating prediabetes. These medications block the reabsorption of sugar from the kidney, so you lose a lot of sugar in your urine. As a result, they lower your blood glucose levels and reduce the amount of insulin your body needs to produce. 

Regularly and carefully monitoring your blood glucose levels can ensure your blood sugar remains within the target range. It shows you whether the changes you are making are working, so you can make adjustments until you find what works best. The number of times you check your blood sugar level can depend on the recommendations of your diabetes nurse or endocrinologist. 

How to prevent prediabetes 

You should maintain a healthy lifestyle to reduce your risk of developing prediabetes. Here are some lifestyle modifications to consider:

Maintain a moderate weight

Try to maintain a healthy weight to reduce the risk of insulin resistance, thus lowering your risk of developing prediabetes. Regular exercise can help you maintain a healthy weight.

Check your diet

Avoid consuming processed meat, red meat, and drinking sweetened beverages as they may increase your risk of developing prediabetes. Consider switching to fiber-rich foods and complex carbohydrates such as whole grain bread, carrot sticks, and fresh fruits instead of simple carbs such as white bread, cookies, and ice cream. 

Avoid smoking

Tobacco use may increase insulin resistance, putting you at risk of developing prediabetes. You can seek your doctor's advice on quitting. 

Exercise regularly

You use more glucose during physical activity, lowering your blood sugar levels. Regular exercise can also help you maintain a moderate weight.  

The lowdown

If you're diagnosed with prediabetes, you can still reverse the condition and get your blood sugar levels back to normal. However, you need early treatment to prevent it from progressing to type 2 diabetes or causing other health complications like stroke and heart disease. 

Lifestyles changes such as healthy dietary changes and getting regular exercise can manage prediabetes. Your doctor can also prescribe medication to prevent prediabetes from progressing to type 2 diabetes. 

If you don't have prediabetes, you can prevent this condition by eating healthy, staying fit, losing weight, and quitting smoking.

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