Diabetes is a chronic condition that affects an estimated 38.4 million people in the United States, and in the last 20 years, the number of diagnoses has more than doubled.

“There are many forms of diabetes and ways patients can arrive at a diagnosis,” explains Dr. Laura Alonso, chief of the Division of Endocrinology, Diabetes, and Metabolism at NewYork-Presbyterian/Weill Cornell Medical Center. “Fundamentally, diabetes is about having a healthy level of blood sugar. Sugar is essential for the body — it provides fuel for muscles when you’re exercising and it’s very important for the brain. On the other hand, high blood sugar can damage organs like your heart, kidneys, eyes, and nerves. So, if your blood sugar goes too low or too high, that can be problematic.”

Health Matters spoke with Dr. Alonso to better understand the early warning signs of diabetes, the different types, how to spot the symptoms, and how it is diagnosed and treated.

What is diabetes?

Dr. Alonso: Diabetes occurs when the body is unable to regulate blood glucose, more commonly referred to as blood sugar.

Sugar in the bloodstream comes from a couple of different sources. When you eat carbohydrates or simple sugars, the sugar is extracted by our intestines and enters the bloodstream. The body also produces sugar, specifically the liver. Between meals and overnight, when sugar levels would otherwise become low, the liver releases sugar into our blood so that our body has the energy that it needs.

To maintain healthy blood sugar levels, cells in our pancreas put a hormone called insulin into our bloodstream. Insulin helps the tissues of the body (like the liver, muscles and fat cells) take up the sugar and use it as fuel — so if the pancreas does not produce enough insulin, or the body does not respond to the insulin properly, it causes diabetes. Sometimes, diabetes is caused when the liver makes too much sugar.

What are the different types of diabetes?

• Type 1
  In people with type 1 diabetes, the immune system attacks the cells in the pancreas that release insulin. If type 1 has been present for a long time, insulin may decline essentially to zero. As a result, the body will not be able to get extra sugar out of the bloodstream and be used as energy.
  
• Type 2
  Type 2 diabetesis the most common (about 90% to 95% of all cases in people is this form of the disease). It is associated with insulin resistance, which means insulin can be made, but the body is not responding to insulin properly.
  
• Gestational
  Gestational diabetes occurs during pregnancy and is caused in part by the placenta that releases hormones that leads to high blood sugar. It goes away completely after delivery of the baby plus the placenta. (Every year, about 5% to 9% of U.S. pregnancies are affected by gestational diabetes.) Women who have had gestational diabetes have an increased risk of getting type 2 diabetes later in life.
  
• Monogenic
  A rare form of diabetes, monogenic diabetes is caused by a single gene mutation. There are probably 15 or more known genes that cause diabetes when there is a mutation. Gene testing for monogenic diabetes is available and helpful because there are certain types of monogenic diabetes where the blood sugar only goes up a little, never leads to hospitalization, and doesn’t cause any harm to the body. Gene testing can also help guide which medication will be the most helpful.

What causes diabetes?

Risk factors for type 2 diabetes include:

• Being overweight
• Having a family history of diabetes
• Not exercising
• Being 45 or older

Type 1 diabetes is more common in children, teenagers, and young adults. Some people have genes from a parent that make them more likely to develop type 1, but even if they have the genes, many will not go on to be diagnosed.

For gestational diabetes, patients who had the condition in a previous pregnancy, have given birth to a baby who weighed 9 pounds, and are overweight are at higher risk. A family history of type 2 diabetes and polycystic ovary syndrome also increases risk.

What are the symptoms and signs of diabetes?

The classic symptoms of diabetes include:

• Excess urination (polyuria)
• Excess thirst (polydipsia)
• Weight loss
• Dehydration
• Feeling very hungry or tired
• Blurry vision

Other symptoms could include sores that heal slowly and more infections than usual, especially urine infections or genital yeast infections. People can also have skin tags, which is a sign of insulin resistance, or thickening of the skin in the back of the neck.

Can diabetes be prevented or reversed?

Prediabetes can be reversed, and type 2 diabetes can be prevented through lifestyle changes, including by:

• Eating healthy
• Maintaining a healthy weight
• Engaging in regular physical activity. Part of the reason the risk for type 2 increases with age is in part due to declining muscle mass, so strength building exercise is recommended.

Currently, we do not have the ability to prevent type 1 diabetes, but there is an immunotherapy called Tzield that can delay diagnosis. Tzield, approved by the Food and Drug Administration in 2022, delays the onset of type 1 diabetes by about two years.

How is diabetes diagnosed?

The two main ways that most people are diagnosed:

• A1C test: Measures a person’s average blood sugar level over the past two or three months. If results are less than 5.7%, then they are in the non-diabetic range. Within 5.7% to 6.4% is considered prediabetes, and 6.5% or above is diabetes.

• Fasting blood sugar test: Measures blood sugar after fasting overnight. If fasting blood sugar is less than 100, a person is non-diabetic. Between 100 and 125 is considered pre-diabetes, and over 126 would be within the diabetes range.

For type 1 diabetes, patients are also often tested for autoantibodies, substances that indicate the immune system is attacking the insulin-producing cells. Urine may also be tested for ketones, which are acids made by the body when it burns fat for energy. Ketones in urine suggest insulin deficiency which may mean type 1 diabetes.

How is diabetes treated?

We have better medications and technologies to treat diabetes than ever before. Patients should stay in contact with their health care team to make sure they are on the best treatment that fits their needs.

The main treatments are:

• Insulin: There are many technologies that patients can chose from to receive insulin, such as smart insulin pen devices where a patient can inject it, and insulin pumps, which delivers it subcutaneously by a small computer.

• Oral and non-insulin injectable medications: For type 2 diabetes, an older medication with decades of safety data is metformin, which helps control the amount of sugar in the blood and improves the body’s response to insulin. Newer “SGLT2” oral medications lower blood sugar while also protecting the kidneys and heart.

• GLP-1 receptor agonists and dual GLP-1/GIP receptor agonists such as Ozempic and Mounjaro lower the blood sugar, protect the kidneys and heart, and also help with weight loss and other metabolism related disorders such as fatty liver and sleep apnea.

What are the complications of diabetes?

For complications, there is a distinction between acute and longterm health problems.

People may need immediate care when blood sugar levels are very high. This can lead to severe dehydration, confusion, or acidosis — it is mostly a feature of type 1 diabetes. And if a person with no insulin production doesn’t consistently take their insulin, they will likely feel sick and may end up in the hospital.

The most common longterm complications include:

• Heart attacks and strokes
• Kidney damage
• Retinopathy (eye damage, can lead to blindness if untreated)
• Neuropathy (nerve damage, especially to feet)

What should patients keep in mind about diabetes management?

It can be helpful to monitor your blood sugar levels. This can be accomplished either with a blood glucose meter, which uses a drop of blood (retrieved through a finger prick) to check what levels are in any given moment, or through a continuous glucose monitor (CGM) which reads the blood sugar levels all the time.

For people not using insulin, a CGM can provide minute-to-minute feedback on how your activity levels, nutrition, and medications affect your blood sugar. For example, a CGM can help you understand which specific foods raise your blood sugar, or whether going for a walk after dinner improves your blood sugar overnight.

For people using insulin, a CGM can be used to help with insulin dosing. Some CGM devices can be connected to certain insulin pumps to guide insulin dosing, such as turning off the insulin infusion if the blood sugar is dropping and giving extra insulin if the blood sugar is high. CGMs can help with safety because if your blood sugar drops, it can alarm and alert you that you need to treat for low blood sugar (hypoglycemia).

It’s also important to talk with your doctor about approaches to keep your sugar in range, especially if you’re experiencing high or low blood sugars.

When blood sugar is too low, it’s usually because a diabetes medication is not matched to a patient’s situation — for example, when someone takes insulin but eats a smaller than normal meal. In this circumstance, confirm the sugar is low, take 15 grams of glucose (either a glucose tablet or hard candy or juice), and then recheck blood sugar in 15 minutes. If low blood sugar is causing confusion, loss of consciousness or a seizure, call 911. If your medication is causing low blood sugars, reach out to your doctor’s office right away so they can adjust your medication.