What is diabetes mellitus? Types, causes, symptoms, and management

Diabetes mellitus is different from diabetes insipidus. But when people mention "diabetes," they often refer to diabetes mellitus. This is not surprising considering that diabetes insipidus is a rare disorder, while diabetes mellitus affects an estimated 422 million people worldwide. To learn more about this highly prevalent medical condition, read on.

A healthcare professional wearing a handglove using a glucometer to test a patient's blood sample for blood glucose level

Key takeaways:

  • Diabetes mellitus is a chronic health condition that occurs when the blood glucose is high, often because the body cannot utilize insulin properly or because it is unable to make enough insulin.
  • Insulin is a hormone that enables the cells of the body to take in glucose and use it for energy. Without insulin, the cells will be unable to properly utilize insulin, leading to high levels of glucose in the blood.
  • Types of diabetes include type 1 diabetes, type 2 diabetes, gestational diabetes, and prediabetes.
  • While diabetes is a chronic health condition, many people with it live normal lives. Medications are available to help treat this condition, and making changes to certain lifestyle and dietary habits can help manage it too.

Diabetes mellitus, commonly called "diabetes", is a metabolic disease condition marked by an abnormal increase in blood sugar levels. This condition is different from diabetes insipidus, which is a disorder of salt and water metabolism that occurs when the body system cannot regulate how it balances fluid in the body, resulting in frequent urination and excessive thirst.

According to the World Health Organization, an estimated 422 million people in the world live with diabetes mellitus, and in the past three decades, its prevalence has risen significantly in different countries.

But although this condition is a common household name, many people are not accurately informed about it. Many people believe that diabetes is simply caused by consuming foods that belong to the carbohydrate class.

But it's more complex than that. Scientific evidence has shown that while limiting the consumption of refined carbohydrates can help manage diabetes, the primary cause of this condition is an impairment in the secretion or action of a hormone called insulin.

Your healthcare team can help you maintain an optimal blood glucose level by prescribing medications and recommending lifestyle and dietary adjustments.

What causes diabetes mellitus?

Diabetes is caused by an impairment in the production or utilization of the insulin hormone which aids the body in utilizing glucose.

Remember that carbohydrates undergo digestion and are broken down into simple sugar (glucose). Normally, the pancreas (an organ found in the abdominal region) secretes insulin in an adequate amount. Insulin moves glucose into your body cells, where it can be stored or used to generate energy.

Without insulin, your body's cells can't utilize glucose. And since they cannot be moved into the cells where they will be used to generate energy, they accumulate in the blood, causing diabetes.

When you have diabetes, it's either your pancreas cells, which are meant to produce insulin, do not produce them as they ought to (type 1 diabetes), or the cells do actually produce insulin hormone, but somehow, your body is resistant to it (type 2 diabetes). This means that even when insulin is produced, the body still can't use it, which causes sugar to build up in the blood.

Types of diabetes

There are two most common types of diabetes:

  • Type 1 diabetes
  • Type 2 diabetes

Type 1 diabetes (insulin-dependent diabetes)

Type 1 diabetes is an autoimmune disease. Health experts are not sure what exactly causes this, but they do know that in people with this type of diabetes, their immune system attacks and destroys the pancreatic cells responsible for producing insulin. This results in the pancreas producing little or no insulin.

Type 1 diabetes is also called juvenile-onset diabetes, as it often begins in childhood. About 5–10% of people with diabetes have this type of diabetes.

The cause of autoimmunity here is not precisely known; however, it is suggested that genes, pancreatic diseases, and viral conditions may play a role in it. People with this condition will need to get a daily dose of insulin administered into their veins in order to stay alive.

Type 2 diabetes (non-insulin-dependent diabetes)

This type of diabetes occurs when your body becomes resistant to insulin. Glucose can't be moved into the cells, and it builds up in the blood. It is also called adult-onset diabetes, even though in recent years, children and teens have also been diagnosed with this type of diabetes mellitus.

About 90–95% of people with diabetes have type 2 diabetes. In this case, the pancreas does secrete some insulin, but it is either insufficient or the body doesn't use it as it should.

Factors that can contribute to type 2 diabetes include genetic factors, lifestyle, and being overweight or obese. Even though it is milder than type 1, it can cause significant health complications like kidney failure and damage to nerves, particularly when it's not managed.

Differences between Type 1 and Type 2 diabetes

Here are some major differences between type 1 and type 2 diabetes:

  1. In type 1 diabetes, the pancreas does not produce insulin because the body’s immune system attacks the beta cells of the islet in the pancreas. In type 2, the pancreas either doesn't produce enough insulin or the body becomes resistant to the insulin produced. 
  2. The exact cause of type 1 diabetes is unknown, but autoimmunity, genetics, and environmental factors are believed to play a role. Type 1 diabetes is less common than type 2 diabetes. 
  3. In the case of type 2 diabetes, which is the most common type of diabetes, it is often linked to genetics and lifestyle factors like obesity and a lack of exercise.
  4. Type 1 diabetes typically develops in childhood or adolescence but can also occur in adults. Its symptoms often appear suddenly. Type 2  can develop at any age but is more common in adults. Symptoms may develop gradually and go unnoticed for a long time. 
  5. Type 1 diabetes requires lifelong insulin injections or an insulin pump to manage blood sugar levels. Type 2 may be managed with lifestyle changes like diet and exercise, medications, or a combination of both. In some cases, insulin may also be needed.

Other types of diabetes

Other types of diabetes include:

  • Gestational diabetes: This is abnormally high blood sugar during pregnancy. The placenta sometimes produces insulin-blocking hormones, predisposing a pregnant person to this medical condition. People who are overweight during pregnancy have higher chances of developing this type of diabetes.
  • Neonatal diabetes mellitus: This is a rare condition that can affect newborn babies in their first six months of life. It is also called congenital or early-onset diabetes and is said to have a genetic origin. The condition is characterized by uncontrolled high blood sugar levels and low insulin. Insulin replacement therapy is a treatment option for it.
  • Prediabetes: This is when the blood sugar level is higher than normal—but not high enough to be diagnosed as diabetes. People with this type of diabetes are at a higher risk of developing type 2 diabetes.

It is important to know the type of diabetes you or your loved one has been diagnosed with, and a healthcare professional is the best person to help with that. After a proper diagnosis, your doctor can suggest the best treatment option for your condition.

Symptoms of diabetes

Each type of diabetes has specific symptoms that are unique to it. However, there are still overlapping symptoms that typically present with any type of diabetes. Some of the symptoms are:

  • Increased hunger
  • Intense thirst
  • Changes in weight
  • Extreme fatigue and tiredness
  • Frequent urination
  • Sores that heal slowly or don't heal at all
  • Blurry vision

Do men and women exhibit the same symptoms?

You may be wondering if the symptoms of diabetes are the same for both genders. Both men and women tend to exhibit similar symptoms of diabetes; however, each sex group might exhibit one or more symptoms unique to their sex group.

For instance, those assigned male at birth who develop diabetes may experience symptoms like decreased sexual desire, weak muscle strength, and erectile dysfunction. On the other hand, those assigned female at birth could show symptoms of yeast infections and urinary tract infections.

Complications of diabetes mellitus

Diabetes mellitus is a chronic health condition. This means it doesn't kill immediately. It develops over time, causing damage to several organs and tissues of the body, especially when it is not managed.

The higher the blood glucose level and the longer you live with the condition, the higher your risk of developing certain complications. Health complications associated with diabetes mellitus include:

  • Neuropathy (damage to peripheral nerve cells)
  • Nephropathy (damage to the kidneys)
  • Heart attack and heart diseases
  • Stroke
  • Foot damage, infections, and sores on the limbs that won't heal
  • Retinopathy and loss of vision
  • Hearing loss
  • Skin conditions like fungal and bacterial infection
  • dementia
  • depression

Gestational diabetes can lead to complications such as:

  • Premature birth
  • Stillbirth
  • High weight of the baby at birth
  • Jaundice
  • Low blood sugar
  • Increased risk of the baby being predisposed to diabetes type 2 later in life

How to manage diabetes mellitus

A diabetes mellitus diagnosis isn't a death sentence. Both type 1 and type 2 diabetes can be managed.

However, it can be challenging considering that different things could cause your blood sugar level to fluctuate, such as dietary composition, lifestyle, menstrual cycle, stress, and medications. Treatment and management will also depend on the type of diabetes.

Here are things to do to help manage your health condition:

1. Make dietary changes

Eating healthy is crucial for maintaining a healthy sugar level, whether you have diabetes or not. However, if you have diabetes, you have even more reason to check what you eat, as diabetes is a metabolic disease.

Food affects your blood sugar level, and it is important to understand how to know the type of food to eat, the right combinations, and the quantity to eat. This is where you may need the help of a registered dietitian nutritionist (RDN). An RDN will help you understand your metabolic health and draw up a meal timetable ideal for your condition.

Here are other helpful dietary tips to help you manage your condition:

  • You should avoid sugary and sweetened foods, as they tend to be high in calories and don't offer much nutrition anyway. Since they can cause a spike in blood sugar levels, you might want to limit their consumption.
  • Make your meals well-balanced. Your meals should have a lot of vegetables, fruits, and proteins. You don't have to totally cut off carbohydrates, but go for the healthy ones that are unrefined, like whole grains.
  • Talk to your doctor or a dietitian about the best food choices for you. Keep in mind that strictly limiting carbohydrate intake in addition to taking a diabetes medication may lead to an abnormally low glucose level (hypoglycemia), which is another dangerous health condition.

2. Exercise

A sedentary lifestyle could predispose one to other health conditions, such as cardiovascular diseases. Exercise helps keep you healthy and is an integral part of your diabetes management plan.

When you work out, your muscles utilize glucose better, which also helps the body make use of insulin more efficiently.

3. Avoid alcohol

It would be best if you were careful when choosing your drinks. Even if you have to take alcohol, it should be done moderately. Alcohol does worsen the complications of diabetes, such as retinopathy and neuropathy. It can increase your blood sugar levels and blood pressure.

4. Avoid stress

Life is full of stressful events, but you have to do your best to avoid putting your body through those stressful situations.

When you are stressed, the body releases certain hormones, such as cortisol and adrenaline, which make it harder for insulin to work properly, ultimately leading to high sugar levels in the blood. Also, when you are always under stress, you may find it harder to follow your diabetes management routine properly.

5. Take your prescribed drugs and monitor your blood glucose level

Your doctor will definitely prescribe drugs to help manage your condition, depending on the type of diabetes. Ensure that you take the medications at the right dosage.

Also, you should check your blood glucose level regularly, just as it is with blood pressure. A sudden spike in the blood sugar level can cause severe damage to essential organs in the body.


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  3. Center for Disease Control and Prevention. (2023). What is diabetes?
  4. National Institute of Diabetes and Digestive and Kidney Disease. (2023). What is Diabetes?
  5. Diabetes UK. (n.d.). Alcohol and diabetes.
  6. Diabetes UK. (n.d.). Stress and diabetes.