Diabetes: An Overview

Medically Reviewed by Shruthi N, MD on August 16, 2024
12 min read

Diabetes is a disease that involves problems with the way your body makes or manages the hormone insulin. It's also known as diabetes mellitus. Normally, your pancreas (an organ behind the stomach) releases insulin to help your body store and use the sugar and fat from the food you eat. 

Diabetes happens because of one of the following:

  • Your pancreas does not make any insulin
  • Your pancreas makes very little insulin
  • Your body doesn't respond appropriately to insulin, a condition called "insulin resistance"

Diabetes is a lifelong disease. About 38.4 million Americans have the disease and one quarter (or approximately 8.7 million) are unaware that they have it. An additional 97.6 million people have prediabetes. As yet, there is no cure. People with diabetes need to manage their disease to stay healthy.

To understand why insulin is important in diabetes, it helps to know more about how your body uses food for energy. Your body is made up of millions of cells. To make energy, these cells need food in a very simple form. When you eat or drink, much of your food is broken down into a simple sugar called "glucose." Then, glucose is transported through your bloodstream to the cells of your body where it can be used to provide some of the energy your body needs for daily activities.

The amount of glucose in your bloodstream is regulated by the hormone insulin. Insulin is always being released in small amounts by your pancreas. When the amount of glucose in your blood rises to a certain level, your pancreas will release more insulin to push more glucose into your cells. This causes your blood glucose level to drop.

To keep it from getting too low (hypoglycemia or low blood sugar), your body signals you to eat and releases some glucose stored in your liver.

People with diabetes either don't make insulin or their body's cells are resistant to insulin, leading to high levels of sugar circulating in the blood, called simply high blood sugar. By definition, diabetes is having a blood glucose level of 126 milligrams per deciliter (mg/dL) or more after an overnight fast (not eating anything).

Type 1 diabetes

Type 1 diabetes happens because the insulin-producing cells of the pancreas (called beta cells) are destroyed by the immune system. People with type 1 diabetes produce no insulin and must use insulin injections to control their blood sugar.

Symptoms most commonly start in people under the age of 20 but can develop at any age.

Type 2 diabetes

Unlike people with type 1 diabetes, people with type 2 diabetes produce insulin. However, either it isn't enough or their body is resistant to the insulin. In that situation, not enough glucose gets into the body's cells and it builds up in the bloodstream.

Type 2 diabetes is the most common form of diabetes, affecting more than 36 million Americans. It's the leading cause of diabetes-related complications such as blindness, amputations, and chronic kidney failure requiring dialysis. Type 2 diabetes usually happens in people over age 40 who are overweight, but it can also affect those who aren't overweight. Sometimes referred to as "adult-onset diabetes," type 2 diabetes has started to appear more often in children because of the rise in obesity in young people.

Some people can manage their type 2 diabetes by losing weight, watching their diet, and exercising regularly. Others may also need to take insulin injections or a pill that helps their body use insulin better.

Prediabetes

In the U.S., 97.6 million adults have blood sugar levels that are higher than normal but not high enough to be classified as diabetes. This is called prediabetes, or impaired glucose tolerance. People with prediabetes usually have no symptoms, but it’s almost always there before a person develops type 2 diabetes. Some complications, such as heart disease, can begin even when a person has only prediabetes.

Talk to your doctor to see if you need to be tested for prediabetes. You may be able to prevent type 2 diabetes and lower your risk of complications.

Gestational diabetes

Gestational diabetes is triggered by pregnancy. Hormone changes during pregnancy can affect insulin's ability to work properly. The condition happens in up to 9% of all pregnancies.

You have an increased risk of developing gestational diabetes if you're over 25 years old, were overweight before your pregnancy, have a family history of diabetes, or are Hispanic, Black, Native American, or Asian.

You'll get screened for gestational diabetes during pregnancy. Left untreated, high blood sugar increases the risk of complications for both you and your child.

Usually, blood sugar levels return to normal within 6 weeks of childbirth. However, having had gestational diabetes increases your risk of developing type 2 diabetes later in life.

Type 3 diabetes

Some researchers have suggested that Alzheimer's disease is a form of diabetes that affects the brain, and propose calling it type 3 diabetes. They point to evidence that people with Alzheimer's have insulin resistance in their brains. The connection hasn't been proven, however, and most doctors don't use the term.

Other types of diabetes

There are several less common forms of diabetes, including:

Monogenic diabetes. This includes several different types of diabetes caused by a gene mutation you inherit from one or both of your parents. When it appears in babies, it's called neonatal diabetes mellitus. In older children and young adults, it's called maturity-onset diabetes of the young (MODY).

Type 3c diabetes. This can develop if you've had your pancreas removed, or if it's damaged by illness or injury.

Other types can come from taking steroid medications, having cystic fibrosis, or having certain rare inherited illnesses.

The symptoms of type 1 diabetes often come on suddenly and can be severe. They include:

  • Increased thirst
  • Increased hunger
  • Dry mouth
  • Peeing more than usual
  • Unexplained weight loss 
  • Fatigue (weak, tired feeling)
  • Blurred vision
  • Labored, heavy breathing 
  • Loss of consciousness (rare)

The symptoms of type 2 diabetes may be the same as those of type 1. Most often, there are no symptoms or a very slow development of the above symptoms. Other symptoms may include:

  • Slow-healing sores or cuts
  • Itchy skin (usually in the vaginal or groin area)
  • Rash
  • Yeast infections
  • Numbness or tingling in your hands and feet
  • Impotence or erectile dysfunction

With gestational diabetes, there are often no symptoms. Or you might notice:

  • More thirst
  • More urination
  • More hunger
  • Blurred vision

By itself, pregnancy can make you pee more often and feel hungrier, so these symptoms don’t always mean you have gestational diabetes. But it's important to get tested to avoid problems for both you and your baby.

If you're having symptoms, you should be tested for the disease. Your doctor may also suggest screening if you're at higher risk. The U.S. Preventive Services Task Force recommends you get screened if you're between 35 and 70 years old and have overweight or obesity.

Diabetes is diagnosed by measuring the amount of glucose in your blood. You'll typically need to have high levels on two separate days to get a diagnosis. If you have the disease, measuring your blood sugar is important for keeping it under control. There are several kinds of tests used.

A1c test (glycated hemoglobin)

This test measures the average of your blood sugar levels over 2-3 months. A result of 6.5% or higher means you have diabetes. A level between 5.7% and 6.4% is considered prediabetes. You'll be retested regularly to see whether your treatment plan is working.

Fasting blood sugar test

For this test, you won't be able to eat or drink anything but water for 8 hours before you have your blood drawn. A result of 126 mg/dL or more indicates diabetes. Between 100 mg/dL and 125 mg/dL is prediabetes.

Random blood sugar test

This test can be done at any time, whether you've eaten or not. You may get it if you're having symptoms of diabetes and doctors think it would be dangerous to wait for a fasting test. With this test, 200 mg/dL is considered too high.

Glucose tolerance test

This test takes place over 2 hours, and you'll also have to fast for 8 hours first. Your blood is drawn, and then you drink a very sweet liquid. Your blood is drawn again at 1 hour and 2 hours, and the three results are compared to see how your body manages the sugar. A result above 200 mg/dL at 2 hours means you have diabetes. A level between 140 mg/dL and 199 mg/dL is prediabetes.

A different version of this test that doesn't require you to fast can be used to screen for gestational diabetes. If the result is high, you'll get a more extensive test.

Autoantibody test

This blood test doesn't measure your blood sugar, but it looks for certain immune system proteins that indicate you have type 1 rather than type 2 diabetes. You might get it if a blood sugar test is high, or if you have a parent or sibling with the disease.

Urine ketone test

When you have diabetes, you may need to test your urine for ketones from time to time. These are substances your body makes when it has to use fat rather than glucose for fuel. This can happen when you're low on insulin. Ketones in your urine are a sign of a dangerous condition called ketoacidosis, which needs immediate treatment.

To take the test, you pee in a cup and dip a strip of a special paper into it. The paper changes color to show the level of ketones.

There's no cure for diabetes, but it can be managed and controlled. The goals of managing diabetes are to:

  • Keep your blood sugar levels within a target range.
  • Maintain healthy blood cholesterol and triglyceride levels.
  • Control your blood pressure. Your blood pressure should not go over 130/80.
  • Slow or possibly prevent the development of diabetes-related health problems.

Treatment depends on what type of diabetes you have. It often includes a combination of medications, diet strategies, and lifestyle changes.

An important part of treatment is keeping track of your blood sugar levels. People with type 1 and some people with type 2 diabetes need to test themselves several times a day to make sure their level stays within their target range and take action if it's too high or too low. This might be done by pricking your finger to get a small drop of blood or wearing a monitor that constantly measures your blood sugar through your skin.

People with prediabetes and some people with type 2 diabetes only need their blood tested during checkups, which may be once or several times a year.

Diabetes medications

You may take medication several times a day, or on a daily or weekly schedule.

Insulin. People with type 1 diabetes and some people with type 2 use insulin to allow their cells to absorb glucose. You inject this medication under your skin with a needle and syringe or a special pen. Your doctor will tell you when and how often to take insulin, but it's usually before meals. You could also wear a pump that delivers a steady dose throughout the day. Insulin is safe to take if you have gestational diabetes.

Oral medications. Many people with type 2 diabetes take medication in pill form once or twice a day. You may take a combination of more than one type. These are among the most common:

  • Metformin lowers the amount of glucose your liver makes and helps your body use insulin better. 
  • Sulfonylureas help your body make more insulin.
  • Sodium-glucose cotransporter-2 (SGLT2) inhibitors help your kidneys flush glucose from your blood.
  • Dipeptidyl peptidase-4 (DPP-4) inhibitors boost levels of a naturally occurring hormone that tells your body to release insulin.
  • Thiazolidinediones (TZDs) help your body use insulin better.

Other medications you take by mouth work with your digestion, slowing the breakdown of starches so your blood sugar stays steady.

GLP-1 and GLP-1/GIP receptor agonists. Glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide are naturally occurring hormones that tell your body to release insulin, slow the rate at which food moves out of your stomach, and send signals to your brain that make you feel full.

These drugs mimic the action of those hormones, which helps lower your blood sugar. One medication comes as a pill, while the others you inject under your skin either once a week or once or twice a day. The FDA-approved GLP-1 receptor agonists for type 2 diabetes are:

  • Dulaglutide
  • Exenatide
  • Liraglutide
  • Lixisenatide
  • Semaglutide

Tirzepatide is the only approved dual GLP-1/GIP receptor agonist.

Other medications. To help prevent some of the complications that can come from from diabetes, your doctor may also prescribe blood pressure or cholesterol medications, or low-dose aspirin.

Diabetes and diet

What and when you eat plays an important part in controlling your blood glucose levels. Certain foods, such as sweets, soft drinks, and refined grains like white bread, are digested very quickly and cause your blood sugar to spike. Skipping a meal can make your blood sugar drop too low.

When you have type 1 diabetes, you need to understand how the things you eat and drink affect your blood sugar, so you can be sure to get the right amount of insulin to stay in your target range. Your doctor will teach you to track nutrients, especially carbohydrates, and adjust your insulin doses.

For everyone with diabetes or prediabetes, following a healthy diet can help you control your blood sugar, cholesterol, blood pressure, and weight. That includes:

  • Fruits and non-starchy vegetables
  • Whole grains
  • Lean meats and dairy foods
  • Foods high in vitamins, minerals, and other nutrients such as calcium, protein, fiber, and healthy fats

Things to limit or avoid include:

  • Sugar-sweetened foods and drinks
  • Alcohol
  • Saturated fat
  • Sodium
  • Refined grains

Diabetes and exercise

Physical activity helps your body use insulin better, which lowers your blood sugar. It can also help you keep your blood pressure and cholesterol down and manage your weight.

Doctors recommend at least 30 minutes of moderate exercise 5 days every week, plus 2 days of strength training. That can be walking at a brisk pace, swimming, or even dancing. Pick something you enjoy and will stick with, and check with your doctor before you start an exercise program.

If you have type 1 diabetes, you may need to change your insulin dose or eat more carbs when you exercise so your blood sugar doesn't drop too low.

Diabetes home remedies

You hold the key to managing your diabetes. Take these steps to help control your blood sugar and prevent complications:

  • Follow your treatment plan.
  • Keep up with regular doctor's appointments and lab tests.
  • Monitor your blood sugar and blood pressure levels at home.
  • Watch for problems with your feet, gums, and eyes.
  • Get vaccinated for the flu, RSV, and COVID-19, as high blood sugar weakens your immune system.
  • Lose weight if you're overweight.
  • Stop smoking.
  • Lower your stress level.
  • Have a plan for low blood sugar emergencies.

Remember: What you do at home every day affects your blood sugar more than what your doctor can do every few months during your checkups.

While you can't prevent type 1 diabetes, you can make lifestyle changes that will lower your risk of developing type 2 diabetes.

  • Eat a healthy diet that includes lots of fruits, vegetables, and whole grains.
  • Avoid sugary, high-calorie foods and drinks.
  • Stay active. Aim for 30 minutes of aerobic exercise 5 days a week.
  • Lose weight if you're overweight.
  • Have your blood sugar tested if you're at higher risk.

Ask your doctor if medications such as metformin or weight loss drugs might be helpful.

Diabetes is a disease in which your body has problems either making or using insulin. That leads to too much glucose (sugar) in your blood, which can cause serious health problems. You can lower your risk for the most common type, type 2 diabetes, by losing weight, being physically active, and following a healthy eating plan. Ask your doctor if you should have a screening blood sugar test.

Can diabetes be reversed?

People with type 2 diabetes can lower their blood sugar to levels that are no longer in the range of diabetes. Doctors call this remission. It's usually accomplished by losing weight. But type 2 diabetes can come back. Type 1 diabetes can't be reversed.

If I have type 2 diabetes and take insulin, do I have to take it forever?

Not necessarily. For some people, insulin is a short-term treatment to quickly lower your blood sugar. If diet, exercise, weight loss, and other medications bring your blood glucose levels under control, you may be able to stop taking insulin.

Do sugary drinks cause diabetes?

Not directly, but a study published in 2019 found an increased risk of developing type 2 diabetes for people who drank 4 ounces of sugar-sweetened drinks, including soft drinks and juice, every day. Sugar from any source raises your blood sugar level. Over time, blood sugar that's too high makes your body less sensitive to insulin.

How can I flush sugar out of my system fast?

Taking fast-acting insulin, drinking water, and exercising can help lower your blood sugar quickly. But exercise is dangerous if you have ketoacidosis, so test your urine for ketones first if your blood sugar level is high. Call your doctor to find out if you need emergency treatment.