Diabetes Mellitus

Diabetes mellitus is a condition that affects how your body manages blood sugar, impacting millions of people of all ages worldwide. While it cannot be cured, it can be effectively managed through a combination of lifestyle changes, medications, and regular monitoring to help you live a healthy, fulfilling life.

What is diabetes mellitus?
Types of diabetes
Symptoms
What causes diabetes?
How is diabetes diagnosed?
Treatment and management
Healthy living with diabetes
Possible complications
Prevention

What is diabetes mellitus?

Diabetes mellitus is a condition that happens when your blood sugar, also called glucose, is too high^[1]. Glucose is your body’s main source of energy and comes from the food you eat, particularly from carbohydrates. Your blood carries glucose to all your body’s cells to use for fuel^[1].

When glucose is in your bloodstream, it needs help to reach its final destination inside your cells. This help comes from a hormone called insulin, which is made by your pancreas, an organ located behind your stomach^[1]. Insulin acts like a key that unlocks your cells so glucose can enter and be used for energy^[9].

Diabetes develops when your pancreas doesn’t make enough insulin or any at all, or when your body isn’t responding to the effects of insulin properly. This is called insulin resistance^[1]. When either of these problems occurs, glucose builds up in your bloodstream instead of entering your cells, causing high blood sugar levels^[2].

Over time, having consistently high blood glucose can cause health problems, such as heart disease, nerve damage, kidney disease, and eye issues^[1]. Diabetes affects people of all ages, and while most forms are chronic, meaning lifelong, all forms are manageable with medications and lifestyle changes^[1].

Types of diabetes

There are several types of diabetes. The most common forms include:

Type 2 diabetes is the most common type. With this form, your body doesn’t make enough insulin and your body’s cells don’t respond normally to the insulin^[1]. It mainly affects adults, but children can have it as well. Type 2 diabetes develops over many years and is usually diagnosed in adults, although more and more children, teens, and young adults are being diagnosed^[2].

Prediabetes is the stage before Type 2 diabetes. Your blood glucose levels are higher than normal but not high enough to be officially diagnosed with Type 2 diabetes^[1]. In the United States, about 1 in 3 adults has prediabetes, and more than 8 in 10 people with prediabetes don’t know they have it^[2]. Prediabetes raises your risk for Type 2 diabetes, heart disease, and stroke, but it can often be reversed with lifestyle changes.

Type 1 diabetes is an autoimmune disease, meaning your immune system mistakenly attacks and destroys the insulin-producing cells in your pancreas^[1]. People with Type 1 diabetes make little or no insulin and need to take insulin every day to survive. Up to 10% of people who have diabetes have Type 1^[1]. It’s usually diagnosed in children and young adults, but it can develop at any age^[2].

Gestational diabetes develops in some people during pregnancy. Gestational diabetes usually goes away after the baby is born^[1]. However, if you have gestational diabetes, you’re at a higher risk of developing Type 2 diabetes later in life. Your baby is also more likely to have obesity as a child or teen and develop Type 2 diabetes later in life^[2].

Other less common types of diabetes include:

Type 3c diabetes happens when your pancreas experiences damage from conditions like pancreatitis, pancreatic cancer, cystic fibrosis, or having your pancreas removed^[1].
Latent autoimmune diabetes in adults (LADA) results from an autoimmune reaction like Type 1 diabetes, but it develops much more slowly. People diagnosed with LADA are usually over the age of 30^[1].
Maturity-onset diabetes of the young (MODY), also called monogenic diabetes, happens due to an inherited genetic mutation that affects how your body makes and uses insulin. It affects up to 5% of people with diabetes and commonly runs in families^[1].
Neonatal diabetes is a rare form that occurs within the first six months of life^[1].

Symptoms

Diabetes symptoms depend on how high your blood sugar is. Some people, especially if they have prediabetes or Type 2 diabetes, may not have symptoms at first^[6]. In Type 1 diabetes, symptoms tend to come on quickly and be more severe^[6].

Common symptoms of Type 1 diabetes and Type 2 diabetes include:

Feeling more thirsty than usual
Urinating often
Losing weight without trying
Feeling tired and weak
Feeling irritable or having other mood changes
Having blurry vision
Having slow-healing sores
Getting a lot of infections, such as gum, skin, and vaginal infections^[6]

People with Type 1 diabetes may also have the presence of ketones in their urine. Ketones are a byproduct of the breakdown of muscle and fat that happens when there’s not enough available insulin^[6].

Symptoms of diabetes may occur suddenly in Type 1, but in Type 2 diabetes, the symptoms can be mild and may take many years to be noticed^[7]. You may not notice any symptoms, so it’s important to get your blood sugar tested if you’re at risk^[2].

What causes diabetes?

The main cause of diabetes varies by type. In Type 1 diabetes, the immune system attacks and destroys the insulin-producing cells in the pancreas for unknown reasons^[1]. This autoimmune reaction stops your body from making insulin^[2]. Currently, no one knows how to prevent Type 1 diabetes.

Type 2 diabetes develops when your body doesn’t use insulin properly, a condition called insulin resistance. As a result, glucose starts to build up in the blood^[9]. The pancreas tries to compensate by making extra insulin to move glucose into the cells. At first, this works, but over time, the body’s insulin resistance gets worse and the pancreas becomes exhausted and cannot keep up with the demand for more insulin^[9].

Several factors can increase your risk for Type 2 diabetes, including:

Being overweight or having obesity
Having a family history of the disease
Being physically inactive
Age (risk increases as you get older)^[8]

Gestational diabetes happens when the body does not respond well to insulin during pregnancy, unless insulin can be produced or provided in larger amounts^[9]. The hormones produced during pregnancy can make your body more resistant to insulin.

How is diabetes diagnosed?

Doctors diagnose diabetes by measuring blood sugar levels using several different tests^[1].

The glycated hemoglobin test, also called the A1C test, is most often used to diagnose Type 2 diabetes. It reflects the average blood sugar level for the past two to three months^[15]. Results mean the following:

Below 5.7% is healthy
5.7% to 6.4% is prediabetes
6.5% or higher on two separate tests means diabetes^[15]

Other tests used to diagnose diabetes include:

Random blood sugar test: A blood sugar level of 200 mg/dL (11.1 mmol/L) or higher suggests diabetes, especially if you also have symptoms like urinating often and being very thirsty^[15].

Fasting blood sugar test: You give a blood sample for testing after not eating overnight. Results are as follows:

Less than 100 mg/dL (5.6 mmol/L) is healthy
100 to 125 mg/dL (5.6 to 6.9 mmol/L) is prediabetes
126 mg/dL (7 mmol/L) or higher on two tests is diabetes^[15]

Oral glucose tolerance test: You don’t eat for a certain amount of time, then you drink a sugary liquid. Blood samples are taken over two hours to test blood sugar levels. A result of 200 mg/dL (11.1 mmol/L) or higher after two hours suggests diabetes^[15].

The American Diabetes Association suggests that all adults age 35 or older have routine tests for Type 2 diabetes^[15]. Testing may also be recommended for younger people who have risk factors such as being overweight or having a family history of diabetes.

Treatment and management

The goals in caring for patients with diabetes are to eliminate symptoms and to prevent or slow the development of complications^[13]. Treatment involves multiple approaches, including glycemia control, managing blood pressure and cholesterol, and regular monitoring for complications.

Ideally, blood glucose should be maintained at near-normal levels, with preprandial levels of 90 to 130 mg/dL and A1C levels less than 7%^[13]. However, treatment goals may be adjusted based on individual factors such as age, other health conditions, and risk of low blood sugar.

Medications for diabetes

The medicine you take depends on the type of diabetes you have and how well the medicine controls your blood glucose levels^[12].

Type 1 diabetes treatment: If you have Type 1 diabetes, you must take insulin because your pancreas does not make it. You will need to take insulin several times during the day, including when you eat and drink^[12]. There are different ways to take insulin, including using a needle and syringe, an insulin pen, or an insulin pump^[12].

Type 2 diabetes treatment: If you have Type 2 diabetes and need medicine, you’ll usually be offered metformin first, which is one of a few medicines used to treat Type 2 diabetes^[17]. Metformin is part of a group of drugs called biguanides, which help lower blood glucose levels.

If metformin alone does not lower your blood glucose level, or if you have another health problem, you may need to take another medicine with metformin or change to a different diabetes medicine^[17]. Other types of medicines for Type 2 diabetes include:

Glucagon-like peptide-1 (GLP-1) agonists, which are injectable medicines that help your body produce more insulin when blood sugar is high
SGLT2 inhibitors, which help your kidneys remove sugar from your body through urine
DPP-4 inhibitors, which help your body produce more insulin after meals
Sulfonylureas, which help your pancreas release more insulin
Thiazolidinediones, which help insulin work better in your body^[14]

If diabetes medicines do not help enough, you may need to take insulin. Some people with Type 2 diabetes may eventually need insulin to maintain blood glucose control^[17].

It’s very important to take your diabetes medications as recommended by your doctor. Left untreated, diabetes can lead to serious complications such as kidney disease, blindness, the need for amputation, and even death from cardiovascular disease^[16].

Monitoring blood glucose

Monitoring your blood sugar is very important to living with diabetes. If your levels are too low, it can impact your ability to think and function. If they are too high, it can damage your body over time^[23].

There are several ways to monitor your blood glucose:

A blood glucose test tells you your blood sugar levels at that moment. These typically involve poking your fingertip and testing your blood in a blood glucose meter^[23].
An A1C test reads your average blood sugar levels over the last three months. This test helps you and your care team manage your diabetes by getting a broader picture of your health^[23].
Continuous glucose monitoring (CGM) involves a sensor inserted under your skin that automatically measures blood sugar throughout the day and night. With CGM, many patients are comforted in knowing that if they do have low glucose, they will be alerted and can then address it^[23].

Healthy living with diabetes

Two of the greatest tools you have for managing your diabetes are diet and exercise. Together, they can help you control your blood sugar and maintain a consistent level of energy^[23].

Healthy eating

What you choose to eat, how much you eat, and when you eat are important parts of a meal plan for diabetes^[26]. Having healthy foods and drinks can help keep your blood glucose, blood pressure, and cholesterol levels in the ranges your health care professional recommends.

There is no single diet that works for everyone with diabetes. However, some general tips include:

Do not skip meals. Consistent nutrition is key to your health^[23].
Incorporate different foods into your diet. Make meals with whole grains, fruits, vegetables, healthy fats, and lean meats or meat substitutes^[23].
Count your carbs. When you have diabetes, your body doesn’t digest carbs properly, and too many carbs can increase your blood sugar levels. Tracking your carb consumption can help you match your medicine and activity to what you eat^[23].
Choose whole grain breads, cereals, and pasta. Whole grains have more fiber and take longer to digest than white flour and other refined starches, which can help keep your blood sugar levels steadier^[25].
Eat a wide variety of low-calorie produce. Choose bright or deep-colored fruits and vegetables such as spinach, tomatoes, carrots, broccoli, squash, or sweet potatoes^[25].
Avoid sugary drinks and foods. Drink water or unsweetened tea instead of soft drinks or other beverages high in natural or added sugar^[25].
Practice moderation. Space your meals evenly throughout the day and try not to eat too much food^[23].

Physical activity

Regular exercise helps control blood sugar levels and makes your body more sensitive to insulin, which can help you manage diabetes^[12]. Additionally, physical activity helps to relieve stress, keep your joints healthy, and lower risk for heart disease and stroke^[23].

Even small increases in physical activity can help you control your blood sugar and blood pressure levels^[25]. Talk to your healthcare provider about how to get started if you haven’t been exercising for a while. If your healthcare provider says it is safe, start with at least 20 minutes of exercise at least three times a week^[25].

Some types of exercise you can try include aerobic activities such as walking, biking, and swimming^[23]. Find ways to be active throughout the day, like climbing stairs or working out with a friend^[18].

Weight management

If you are overweight, losing even 5 to 10 pounds can help make your diabetes easier to treat^[25]. You can do this by both eating well and exercising regularly. A healthy meal plan along with regular physical activity, getting enough sleep, and other healthy behaviors may help you reach and maintain a healthy weight^[26].

Other important lifestyle factors

Managing diabetes also involves:

Getting enough sleep: Adequate rest is important for blood sugar control and overall health^[18].
Managing stress: Stress can cause your blood sugar to rise. Find activities you like that help you relax, such as taking a walk, listening to your favorite music, or trying meditation or yoga^[22].
Quitting smoking: Having diabetes increases the harmful effects of smoking. Avoiding tobacco use is important for preventing complications^[7].
Limiting alcohol: Drinking alcohol can produce signs of low blood sugar. When you drink, your liver works to process the alcohol, which can mean it’s too busy to perform another important function: releasing stored sugar in response to low levels^[22].
Practicing good oral hygiene: Diabetes puts you at greater risk for gum disease because people with diabetes have a lowered ability to fight infection from bacteria in the mouth^[22].

Regular check-ups

If you have diabetes, you’ll need check-ups to make sure your treatment is working and your condition is being managed. These include:

Checking your average blood glucose levels (an A1C test) every 3 to 6 months
A foot check-up once every 2 years if your last check was OK, or once a year if you need it
Checking your weight, body mass index (BMI), cholesterol, blood pressure, and kidneys at least once a year
Diabetic eye screening when you’re diagnosed, and reviewed every 1 or 2 years^[17]

Possible complications

Over time, having consistently high blood glucose can cause serious health problems^[1]. Diabetes can affect almost every part of your body.

Common complications of diabetes include:

Heart disease and stroke: Diabetes can damage blood vessels and increase the risk of heart attack and stroke^[3]. In 2021, high blood glucose causes around 11% of cardiovascular deaths^[7].
Kidney disease: Diabetes is a leading cause of chronic kidney disease. In 2021, diabetes and kidney disease due to diabetes caused over 2 million deaths^[7].
Eye problems: Diabetes can damage blood vessels in the eyes and cause vision loss or blindness^[7].
Nerve damage: High blood sugar can damage nerves throughout your body, causing problems with the sense of touch, pain, and other sensations^[3].
Foot problems: Nerve damage and poor blood flow can lead to serious foot infections and, in severe cases, amputation.
Gum disease and other dental problems: People with diabetes are at higher risk for infections in the mouth^[1].

Taking steps to manage diabetes can help lower your risk of developing these health problems. By keeping your blood glucose, blood pressure, and cholesterol levels under control, you can prevent or delay complications^[3].

Prevention

Type 1 diabetes cannot currently be prevented because no one knows what causes the autoimmune reaction^[2]. However, Type 2 diabetes can often be prevented or delayed through lifestyle changes.

A healthy diet, regular physical activity, maintaining a normal body weight, and avoiding tobacco use are ways to prevent or delay the onset of Type 2 diabetes^[7].

If you have prediabetes, losing weight, eating healthy food, and being active can really help prevent or delay Type 2 diabetes^[2]. About 1 in 3 adults has prediabetes, which is a condition in which blood glucose levels are too high to be considered normal but not high enough to be labeled diabetes^[3].

Steps you can take to prevent Type 2 diabetes include:

Maintaining a healthy weight or losing 5 to 10 pounds if you are overweight
Being physically active for at least 150 minutes per week
Eating a healthy diet that includes whole grains, fruits, vegetables, and limits processed foods and added sugars
Not smoking or using tobacco products
Getting regular check-ups and screenings, especially if you are age 35 or older or have risk factors for diabetes

In the United States, about 1 in 3 adults has prediabetes, and more than 8 in 10 people with prediabetes don’t know they have it^[2]. Getting tested is an important first step in prevention.

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