Diagnosis of type 1 diabetes in adults

Last reviewed: 22 Sep 2022

Last updated: 06 May 2022

Summary

Type 1 diabetes mellitus is a metabolic disorder characterized by hyperglycemia due to absolute insulin deficiency.

Patients most often present with a few days or weeks of polyuria, polydipsia, weight loss, and weakness.

Some patients may present with diabetic ketoacidosis.

Insulin is required for the treatment of type 1 diabetes.

Intensive glycemic control has been shown to decrease the incidence of microvascular and macrovascular complications.

Microvascular complications include retinopathy, nephropathy, and neuropathy.

Macrovascular complications include coronary artery, cerebrovascular, and peripheral vascular disease.

Definition

Type 1 diabetes mellitus is a metabolic disorder characterized by hyperglycemia due to absolute insulin deficiency. The condition develops due to destruction of pancreatic beta cells, mostly by immune-mediated mechanisms. In some patients there may be no evidence of autoimmune destruction of pancreatic beta cells; this is called idiopathic type 1 diabetes.

History and exam

Key diagnostic factors

• polyuria
• polydipsia
• diabetic ketoacidosis

More key diagnostic factors

Other diagnostic factors

• young age
• weight loss
• blurred vision
• nausea and vomiting
• abdominal pain
• tachypnea
• lethargy
• altered mental status

Other diagnostic factors

Risk factors

• genetic predisposition
• geographic region
• infectious agents
• dietary factors
• drug-induced

More risk factors

Diagnostic investigations

1st investigations to order

• random plasma glucose
• fasting plasma glucose
• 2-hour plasma glucose
• HbA1c

More 1st investigations to order

Investigations to consider

• plasma or urine ketones
• fasting C-peptide
• autoimmune markers

More investigations to consider

Treatment algorithm

nonpregnant

pregnant

Contributors

Authors

Rajesh K. Garg, MD

Professor of Medicine

University of Miami, Miller School of Medicine

Miami

FL

RKG is an author of a number of references cited in this topic.

Acknowledgements

Dr Rajesh K. Garg would like to gratefully acknowledge Dr Varsha Vimalananda, previous contributor to this topic.

VV declares that she has no competing interests.

Peer reviewers

Zachary Bloomgarden, MD

Clinical Professor

Medicine/Endocrinology

Diabetes and Bone Disease

Mount Sinai School of Medicine

New York

NY

ZB declares that he has no competing interests.

Alicia Jenkins, MB, BS, MD, FRACP, FRCP

Associate Professor

Department of Medicine

University of Melbourne

Melbourne

Australia

Professor

Harold Hamm Oklahoma Diabetes Center

University of Oklahoma Health Sciences Center

Oklahoma City

OK

AJ has been a (non-salaried) co-investigator on multi-center clinical trials supported by Novo, Eli Lilly, Sanofi-Aventis, and Medtronic. She does not hold any stocks or shares in these companies. She has received a speaker's honorarium from Novo Nordisk.

• Differentials

  • Monogenic diabetes: maturity onset diabetes of the young
  • Monogenic diabetes: neonatal diabetes
  • Latent autoimmune diabetes in adults (LADA)

  More Differentials

• Guidelines

  • Standards of medical care in diabetes - 2022
  • Clinical practice guidelines for the prevention and management of diabetes in Canada

  More Guidelines

• Patient leaflets

  Diabetes type 1: what is it?

  Diabetes type 1: what treatments work?

  More Patient leaflets

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People of all ages can develop type 1 diabetes.

If you have type 1 diabetes, your pancreas doesn’t make insulin or makes very little insulin. Insulin helps blood sugar enter the cells in your body for use as energy. Without insulin, blood sugar can’t get into cells and builds up in the bloodstream. High blood sugar is damaging to the body and causes many of the symptoms and complications of diabetes.

Type 1 diabetes was once called insulin-dependent or juvenile diabetes. It usually develops in children, teens, and young adults, but it can happen at any age.

Type 1 diabetes is less common than type 2—about 5-10% of people with diabetes have type 1. Currently, no one knows how to prevent type 1 diabetes, but it can be treated successfully by:

• Following your doctor’s recommendations for living a healthy lifestyle.
• Managing your blood sugar.
• Getting regular health checkups.
• Getting diabetes self-management education and support.

If your child has type 1 diabetes—especially a young child—you’ll handle diabetes care on a day-to-day basis. Daily care will include serving healthy foods, giving insulin injections, and watching for and treating hypoglycemia (low blood sugar). You’ll also need to stay in close contact with your child’s health care team. They will help you understand the treatment plan and how to help your child stay healthy.

Much of the information that follows applies to children as well as adults. You can also visit JDRF’s T1D Resourcesexternal icon for more information on managing your child’s type 1 diabetes.

What Causes Type 1 Diabetes?

Type 1 diabetes is thought to be caused by an autoimmune reaction (the body attacks itself by mistake). This reaction destroys the cells in the pancreas that make insulin, called beta cells. This process can go on for months or years before any symptoms appear.

Some people have certain genes (traits passed on from parent to child) that make them more likely to develop type 1 diabetes. However, many of them won’t go on to have type 1 diabetes even if they have the genes. A trigger in the environment, such as a virus, may also play a part in developing type 1 diabetes. Diet and lifestyle habits don’t cause type 1 diabetes.

Symptoms and Risk Factors

It can take months or years before symptoms of type 1 diabetes are noticed. Type 1 diabetes symptoms can develop in just a few weeks or months. Once symptoms appear, they can be severe.

Some type 1 diabetes symptoms are similar to symptoms of other health conditions. Don’t guess! If you think you could have type 1 diabetes, see your doctor to get your blood sugar tested. Untreated diabetes can lead to very serious—even fatal—health problems.

Risk factors for type 1 diabetes are not as clear as for prediabetes and type 2 diabetes. However, studies show that family history plays a part.

Testing for Type 1 Diabetes

A simple blood test will let you know if you have diabetes. If you were tested at a health fair or pharmacy, follow up at a clinic or doctor’s office. That way you’ll be sure the results are accurate.

If your doctor thinks you have type 1 diabetes, your blood may also be tested for autoantibodies. These substances indicate your body is attacking itself and are often found with type 1 diabetes but not with type 2. You may have your urine tested for ketones too. Ketones are produced when your body burns fat for energy. Having ketones in your urine indicates you have type 1 diabetes instead of type 2.

Managing Diabetes

Unlike many health conditions, diabetes is managed mostly by you, with support from your health care team:

• Primary care doctor
• Foot doctor
• Dentist
• Eye doctor
• Registered dietitian nutritionist
• Diabetes educator
• Pharmacist

Also ask your family, teachers, and other important people in your life for help and support. Managing diabetes can be challenging, but everything you do to improve your health is worth it!

If you have type 1 diabetes, you’ll need to take insulin shots (or wear an insulin pump) every day. Insulin is needed to manage your blood sugar levels and give your body energy. You can’t take insulin as a pill. That’s because the acid in your stomach would destroy it before it could get into your bloodstream. Your doctor will work with you to figure out the most effective type and dosage of insulin for you.

You’ll also need to do regular blood sugar checks. Ask your doctor how often you should check it and what your target blood sugar levels should be. Keeping your blood sugar levels as close to target as possible will help you prevent or delay diabetes-related complications.

Stress is a part of life, but it can make managing diabetes harder. Both managing your blood sugar levels and dealing with daily diabetes care can be tougher to do. Regular physical activity, getting enough sleep, and exercises to relax can help. Talk to your doctor and diabetes educator about these and other ways you can manage stress.

Healthy lifestyle habits are really important too:

• Making healthy food choices
• Being physically active
• Controlling your blood pressure
• Controlling your cholesterol

Make regular appointments with your health care team. They’ll help you stay on track with your treatment plan and offer new ideas and strategies if needed.

Hypoglycemia and Diabetic Ketoacidosis

These 2 conditions are common complications of diabetes, and you’ll need to know how to handle them. Meet with your doctor for step-by-step instructions. You may want to bring a family member with you to the appointment so they learn the steps too.

Hypoglycemia (low blood sugar) can happen quickly and needs to be treated quickly. It’s most often caused by:

• Too much insulin.
• Waiting too long for a meal or snack.
• Not eating enough.
• Getting extra physical activity.

Talk to your doctor if you have low blood sugar several times a week. Your treatment plan may need to be changed.

Diabetic ketoacidosis (DKA) is a serious complication of diabetes that can be life-threatening. DKA develops when you don’t have enough insulin to let blood sugar into your cells. Very high blood sugar and low insulin levels lead to DKA. The two most common causes are illness and missing insulin shots. Talk with your doctor and make sure you understand how you can prevent and treat DKA.

Get Diabetes Education

Meeting with a diabetes educator is a great way to get support and guidance, including how to:

• Develop and stick to a healthy eating and activity plan
• Test your blood sugar and keep a record of the results
• Recognize the signs of high or low blood sugar and what to do about it
• Give yourself insulin by syringe, pen, or pump
• Monitor your feet, skin, and eyes to catch problems early
• Buy diabetes supplies and store them properly
• Manage stress and deal with daily diabetes care

Ask your doctor about diabetes self-management education and support services and to recommend a diabetes educator. You can also search this nationwide directoryexternal icon for a list of programs in your community.

Get Support

Tap into online diabetes communities for encouragement, insights, and support. Check out the American Diabetes Association’s Community pageexternal icon and JDRF’s TypeOneNationexternal icon. Both are great ways to connect with others who share your experience.

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