Diabetes Mellitus: Causes, Symptoms, and Treatment
Medically reviewed by Achuta Uppu, MD, Internal Medicine. Last reviewed: October 23, 2026.
What kind of doctor treats Diabetes Mellitus?
A primary care doctor often diagnoses diabetes and manages it over time. An endocrinologist, a doctor who treats hormone and diabetes problems, may help with harder cases. A direct primary care or concierge doctor can be a first stop for an evaluation and can refer you to a specialist when needed.
What is diabetes mellitus?
Diabetes mellitus, usually called diabetes, is a disease in which your blood sugar levels are too high. Blood sugar is also called glucose.
Insulin is a hormone made by your pancreas. Insulin helps move glucose from your blood into your cells, where it is used for energy.
With diabetes, your body can't make insulin, can't use it as well as it should, or both. Over time, high blood sugar can lead to serious health problems.
There are different types of diabetes:
- Type 1 diabetes. Your body makes little or no insulin.
- Type 2 diabetes. This is the most common form. Your cells do not respond well to insulin.
- Gestational diabetes. This form develops during pregnancy.
Symptoms
The symptoms of diabetes may include:
- Feeling very thirsty.
- Feeling very hungry.
- Peeing more often, including at night.
- Fatigue (feeling very tired).
- Blurry vision.
- Numbness or tingling in the feet or hands.
- Sores that do not heal.
- Losing weight without trying.
Symptoms vary by type. Type 1 symptoms usually come on quickly and can be severe. With type 2, symptoms often develop slowly, over several years. They can be so mild that you do not notice. Gestational diabetes often has no symptoms.
Causes and who gets it
Researchers think genes and factors in the environment might trigger type 1 diabetes. In this disease, the immune system attacks and destroys the cells that make insulin.
Type 2 diabetes is caused by several factors, including lifestyle and genes. Lifestyle factors include not being physically active and being overweight. Researchers think gestational diabetes is caused by the hormone changes of pregnancy along with genes and lifestyle.
You can get type 1 diabetes at any age, but it most often starts in childhood. You have a higher chance of type 2 diabetes if you:
- Are overweight or have obesity.
- Have a family history of diabetes.
- Have prediabetes, which means blood sugar is higher than normal but not high enough to be called diabetes.
- Have high blood pressure or polycystic ovary syndrome (PCOS).
How doctors diagnose it
Your provider will use one or more blood sugar tests. One is the A1C test. A urine test alone does not diagnose diabetes.
For a fasting blood sugar test, diabetes is diagnosed at 126 mg/dL or higher on two different tests. For the A1C test, a result of 6.5% or higher means diabetes. A result under 5.7% is normal.
An oral glucose tolerance test checks your blood sugar 2 hours after you drink a special sugar drink.
Pregnant women are usually screened for gestational diabetes between 24 and 28 weeks of pregnancy.
Treatment
Treatment involves managing your blood sugar. If you have type 1 diabetes, you will need daily insulin, by injection or through a special pump. Insulin cannot be taken by mouth, because stomach acid destroys it.
With type 2 diabetes, you may be able to manage or even reverse it with lifestyle changes. The most important approach is being active and eating healthy foods. Some people also need diabetes medicines. If diet and exercise are not enough, your provider may prescribe medicine. You may need insulin if other medicines do not control your blood sugar.
If you have gestational diabetes, healthy eating and regular exercise may lower your glucose.
Checking your blood sugar is an important part of managing diabetes.
When to see a doctor
Call 911 or the local emergency number right away if you have:
- Chest pain or pressure.
- Fainting, confusion, or unconsciousness.
- A seizure.
- Shortness of breath.
- Red, painful skin that is spreading quickly.
Contact your provider if your blood sugar is higher than the goals you and your provider set. Also call about numbness, tingling, or pain in your feet or legs.
Low blood sugar can cause weakness, trembling, and sweating. You can treat early signs at home with orange juice, sugar or candy, or glucose tablets. If signs of low blood sugar continue, go to the emergency room.
How a direct primary care or concierge doctor fits in
A direct primary care doctor charges a flat monthly fee instead of billing insurance, while a concierge doctor usually charges more and often works alongside insurance. A direct primary care doctor can order the blood sugar tests used to diagnose diabetes and do a yearly foot exam. They can also refer you to an eye doctor.
Common questions
Can type 2 diabetes be reversed?
Sometimes. You may be able to manage or even reverse type 2 diabetes with lifestyle changes. Lifestyle changes include healthy eating, a healthy weight, and regular activity. Some people can stop taking medicines after losing weight. This does not mean the diabetes is cured.
Can type 2 diabetes be prevented?
Sometimes. You may be able to delay or prevent type 2 diabetes with a healthy diet, a healthy weight, and regular activity. At this time, type 1 diabetes cannot be prevented. Promising research shows it may be delayed in some high risk people.
Does diabetes always cause symptoms?
No, some people have no symptoms.
What problems can diabetes cause over time?
Diabetes can cause eye problems, including trouble seeing. It can damage nerves, causing pain, tingling, and loss of feeling. It can also raise the chance of a heart attack or stroke.
Sources
- MedlinePlus - Diabetes
- MedlinePlus - Diabetes (Medical Encyclopedia)
- MedlinePlus - Type 2 diabetes (Medical Encyclopedia)
Medical Disclaimer
This content is for general educational and informational purposes only and is not medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment, and reading it does not create a doctor-patient relationship. Always seek the advice of your physician or another qualified health provider with any questions about a medical condition, and never disregard or delay seeking professional advice because of something you read here. If you think you may have a medical emergency, call 911 (or your local emergency number) immediately.
