Diabetes Diagnosis: Comprehensive Guide to Types and Tests

Diabetes is a chronic health condition that affects millions worldwide. Early and accurate diagnosis of diabetes is crucial for effective management and preventing serious complications. This article provides a detailed overview of diabetes diagnosis, including the different types of diabetes, screening guidelines, and various diagnostic tests available.

Understanding Diabetes Diagnosis

Diagnosing diabetes involves identifying elevated blood sugar levels. The symptoms of type 1 diabetes often appear rapidly and are usually the initial trigger for blood sugar testing. However, type 2 diabetes and prediabetes can develop gradually, sometimes with subtle or unnoticeable symptoms. Therefore, the American Diabetes Association (ADA) has established screening guidelines to identify individuals at risk.

Who Should Be Screened for Diabetes?

The ADA recommends diabetes screening for the following groups:

Individuals with a BMI over 25 (or over 23 for Asian Americans), regardless of age, who have additional risk factors such as:
- High blood pressure
- Abnormal cholesterol levels
- Physical inactivity
- Polycystic ovary syndrome (PCOS) history
- Heart disease history
- Family history of diabetes
Everyone aged 35 years or older should undergo an initial blood sugar screening. If results are normal, repeat screening every three years.
Women with a history of gestational diabetes should be screened for diabetes every three years.
Individuals diagnosed with prediabetes should be tested annually.
People with HIV are also advised to be screened for diabetes.

Diagnostic Tests for Diabetes and Prediabetes

Several tests are used for the Diagnosis Of Diabetic conditions, including type 1, type 2 diabetes, and prediabetes. These tests measure blood sugar levels and help determine if an individual meets the diagnostic criteria for diabetes or prediabetes.

A1C Test

The A1C test, also known as the glycated hemoglobin test, provides an average blood sugar level over the past 2 to 3 months. This blood test does not require fasting and measures the percentage of blood sugar attached to hemoglobin, the oxygen-carrying protein in red blood cells.

Diabetes Diagnosis: An A1C level of 6.5% or higher on two separate tests indicates diabetes.
Prediabetes Diagnosis: An A1C level between 5.7% and 6.4% suggests prediabetes.
Normal Range: An A1C level below 5.7% is considered normal.

Random Blood Sugar Test

A random blood sugar test involves taking a blood sample at any time of the day, regardless of when the last meal was consumed.

Diabetes Diagnosis: A blood sugar level of 200 mg/dL (11.1 mmol/L) or higher, regardless of the last meal, suggests diabetes, especially when accompanied by diabetes symptoms like increased thirst and frequent urination.

Fasting Blood Sugar Test

The fasting blood sugar test requires an overnight fast (no food or drink except water for at least 8 hours) before taking a blood sample.

Diabetes Diagnosis: A fasting blood sugar level of 126 mg/dL (7 mmol/L) or higher on two separate tests confirms diabetes.
Prediabetes Diagnosis: A fasting blood sugar level between 100 to 125 mg/dL (5.6 to 6.9 mmol/L) indicates prediabetes.
Normal Range: A fasting blood sugar level less than 100 mg/dL (5.6 mmol/L) is considered normal.

Glucose Tolerance Test

The glucose tolerance test is a more involved test used to diagnosis of diabetic conditions, particularly gestational diabetes and type 2 diabetes. It requires fasting overnight, followed by measuring the fasting blood sugar level. Then, the individual drinks a sugary liquid, and blood sugar levels are tested periodically for the next two hours.

Diabetes Diagnosis: A blood sugar level of 200 mg/dL (11.1 mmol/L) or higher after two hours indicates diabetes.
Prediabetes Diagnosis: A blood sugar level between 140 and 199 mg/dL (7.8 mmol/L and 11.0 mmol/L) after two hours signifies prediabetes.
Normal Range: A blood sugar level less than 140 mg/dL (7.8 mmol/L) is considered normal.

Additional Tests for Type 1 Diabetes Diagnosis

If type 1 diabetes is suspected, healthcare providers may conduct additional tests to confirm the diagnosis of diabetic type 1.

Ketone Test: Urine may be tested for ketones. Ketones are produced when the body breaks down fat for energy due to insufficient insulin, a common occurrence in type 1 diabetes.
Autoantibodies Test: Blood tests can detect autoantibodies, which are destructive immune system cells associated with type 1 diabetes. The presence of these autoantibodies helps differentiate type 1 from type 2 diabetes.

Gestational Diabetes Diagnosis

Screening for gestational diabetes, a type of diabetes that develops during pregnancy, is a routine part of prenatal care.

Early Screening: Women at high risk for gestational diabetes may be screened at their first prenatal visit.
Routine Screening: Women at average risk are typically screened during their second trimester. The glucose tolerance test is commonly used for gestational diabetes diagnosis of diabetic condition in pregnancy.

Managing Diabetes After Diagnosis

Once diagnosis of diabetic condition is confirmed, developing a comprehensive treatment plan is essential. Treatment approaches vary depending on the type of diabetes but generally include:

Lifestyle Modifications: Healthy eating, regular physical activity, and maintaining a healthy weight are fundamental to managing all types of diabetes.
Blood Sugar Monitoring: Regular monitoring of blood sugar levels is critical to managing diabetes effectively and preventing complications.
Medications: Depending on the type of diabetes, treatment may involve insulin therapy (for type 1 and sometimes type 2 and gestational diabetes), oral medications (for type 2 diabetes), or both.

Continuous Glucose Monitoring (CGM)

Alt text: Continuous glucose monitor and insulin pump system for diabetes management.

Continuous glucose monitors (CGMs) are devices that measure blood sugar levels in real-time throughout the day and night. CGMs can significantly improve diabetes management, especially for those using insulin, by providing continuous data to help adjust insulin dosages and lifestyle choices. While CGMs are not a direct diagnosis of diabetic tool, they are invaluable for ongoing management after diagnosis.

Insulin Therapy

For type 1 diabetes, insulin therapy is essential for survival as the body does not produce insulin. Many individuals with type 2 diabetes and gestational diabetes may also require insulin to manage blood sugar levels. Insulin is administered through injections or insulin pumps.

Oral and Injectable Medications for Type 2 Diabetes

Type 2 diabetes management often involves oral medications to improve insulin sensitivity or reduce glucose production by the liver. In some cases, injectable medications, other than insulin, may be used to further manage blood sugar levels.

Pancreas and Islet Cell Transplantation

In certain cases of type 1 diabetes, pancreas transplantation or islet cell transplantation may be considered. These are usually reserved for individuals with poorly controlled type 1 diabetes or those undergoing kidney transplantation due to diabetic kidney disease.

Living Well with Diabetes

A diagnosis of diabetic condition is not the end but the beginning of a journey towards proactive health management. By understanding the diagnosis process, adhering to treatment plans, and adopting healthy lifestyle habits, individuals with diabetes can live full and healthy lives. Regular check-ups with healthcare providers, diabetes educators, and dietitians are crucial for ongoing support and management.

Seeking Expert Care

For comprehensive diabetes care and diagnosis of diabetic concerns, consulting with experts at specialized centers like Mayo Clinic can provide significant benefits. A multidisciplinary team of endocrinologists, diabetes educators, and dietitians can offer personalized treatment plans and support to navigate life with diabetes effectively.

From Mayo Clinic to your inbox

Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. Click here for an email preview.

ErrorEmail field is required

ErrorInclude a valid email address

We use the data you provide to deliver you the content you requested. To provide you with the most relevant and helpful information, we may combine your email and website data with other information we have about you. If you are a Mayo Clinic patient, we will only use your protected health information as outlined in our Notice of Privacy Practices. You may opt out of email communications at any time by clicking on the unsubscribe link in the email.

Thank you for subscribing!

You’ll soon start receiving the latest Mayo Clinic health information you requested in your inbox.

Sorry something went wrong with your subscription

Please, try again in a couple of minutes

Clinical trials

Explore Mayo Clinic studies testing new treatments, interventions and tests as a means to prevent, detect, treat or manage this condition.

Lifestyle and home remedies

Diabetes is a serious disease. Following your diabetes treatment plan takes total commitment. Careful management of diabetes can lower your risk of serious or life-threatening complications.

Commit to managing your diabetes. Learn all you can about diabetes. Build a relationship with a diabetes educator. Ask your diabetes treatment team for help when you need it.
Choose healthy foods and stay at a healthy weight. If you’re overweight, losing just 7% of your body weight can make a difference in your blood sugar control if you have prediabetes or type 2 diabetes. A healthy diet is one with plenty of fruits, vegetables, lean proteins, whole grains and legumes. And limit how much food with saturated fat you eat.
Make physical activity part of your daily routine. Regular physical activity can help prevent prediabetes and type 2 diabetes. It can also help those who already have diabetes to maintain better blood sugar control. A minimum of 30 minutes of moderate physical activity — such as brisk walking — most days of the week is recommended. Aim for at least 150 minutes of moderate aerobic physical activity a week.

Getting regular aerobic exercise along with getting at least two days a week of strength training exercises can help control blood sugar more effectively than does either type of exercise alone. Aerobic exercises can include walking, biking or dancing. Resistance training can include weight training and body weight exercises.

Also try to spend less time sitting still. Try to get up and move around for a few minutes at least every 30 minutes or so when you’re awake.

Lifestyle recommendations for type 1 and type 2 diabetes

Also, if you have type 1 or type 2 diabetes:

Identify yourself. Wear a tag or bracelet that says you have diabetes. Keep a glucagon kit nearby in case of a low blood sugar emergency. Make sure your friends and loved ones know how to use it.
Schedule a yearly physical and regular eye exams. Your regular diabetes checkups aren’t meant to replace yearly physicals or routine eye exams. During the physical, your provider will look for any diabetes-related complications and screen for other medical problems. Your eye care specialist will check for signs of eye damage, including retinal damage (retinopathy), cataracts and glaucoma.
Keep your vaccinations up to date. High blood sugar can weaken your immune system. Get a flu shot every year. Your provider may recommend the pneumonia and COVID-19 vaccines, as well.

The Centers for Disease Control and Prevention (CDC) also currently recommends hepatitis B vaccination if you haven’t previously had it and you’re an adult ages 19 to 59 with type 1 or type 2 diabetes.

The most recent CDC guidelines suggest vaccination as soon as possible after diagnosis with type 1 or type 2 diabetes. If you are age 60 or older, have been diagnosed with diabetes, and haven’t previously received the vaccine, talk to your provider about whether it’s right for you.
Pay attention to your feet. Wash your feet daily in lukewarm water. Dry them gently, especially between the toes. Moisturize with lotion, but not between the toes. Check your feet every day for blisters, cuts, sores, redness or swelling. Talk to your provider if you have a sore or other foot problem that doesn’t heal quickly on its own.
Control your blood pressure and cholesterol. Eating healthy foods and exercising regularly can help control high blood pressure and cholesterol. Drugs may be needed, too.
Take care of your teeth. Diabetes may leave you prone to more-serious gum infections. Brush and floss your teeth at least twice a day. And if you have type 1 or type 2 diabetes, schedule regular dental exams. Talk to your dentist right away if your gums bleed or look red or swollen.
If you smoke or use other types of tobacco, ask your provider to help you quit. Smoking increases your risk of many diabetes complications. Smokers who have diabetes are more likely to die of cardiovascular disease than are nonsmokers who have diabetes. Talk to your provider about ways to stop smoking or to stop using other types of tobacco.
If you drink alcohol, do so responsibly. Alcohol can cause either high or low blood sugar. This depends on how much you drink and if you eat at the same time. If you choose to drink, do so only in moderation — one drink a day for women and up to two drinks a day for men — and always with food.

Remember to include the carbohydrates from any alcohol you drink in your daily carbohydrate count. And check your blood sugar levels before going to bed.
Take stress seriously. The hormones your body may make in response to long-term stress may prevent insulin from working properly. This will raise your blood sugar and stress you even more. Set limits for yourself and prioritize your tasks. Learn relaxation techniques. And get plenty of sleep.

Alternative medicine

Many substances have been shown to improve the body’s ability to process insulin in some studies. Other studies fail to find any benefit for blood sugar control or in lowering A1C levels. Because of the conflicting findings, there aren’t any alternative therapies that are currently recommended to help everyone to manage blood sugar.

If you decide to try any type of alternative therapy, don’t stop taking the drugs that your provider has prescribed. Be sure to discuss the use of any of these therapies with your provider. Make sure that they won’t cause bad reactions or interact with your current therapy.

Also, no treatments — alternative or conventional — can cure diabetes. If you’re using insulin therapy for diabetes, never stop using insulin unless directed to do so by your provider.

Coping and support

Living with diabetes can be difficult and frustrating. Sometimes, even when you’ve done everything right, your blood sugar levels may rise. But stick with your diabetes management plan and you’ll likely see a positive difference in your A1C when you visit your provider.

Good diabetes management can take a great deal of time and feel overwhelming. Some people find that it helps to talk to someone. Your provider can probably recommend a mental health professional for you to speak with. Or you may want to try a support group.

Sharing your frustrations and triumphs with people who understand what you’re going through can be very helpful. And you may find that others have great tips to share about diabetes management.

Your provider may know of a local support group. You can also call the American Diabetes Association at 800-DIABETES (800-342-2383) or the Juvenile Diabetes Research Foundation at 800-533-CURE (800-533-2873).

Preparing for your appointment

You’re likely to start by seeing your health care provider if you’re having diabetes symptoms. If your child is having diabetes symptoms, you might see your child’s health care provider. If blood sugar levels are very high, you’ll likely be sent to the emergency room.

If blood sugar levels aren’t high enough to put you or your child immediately at risk, you may be referred to a provider trained in diagnosing and treating diabetes (endocrinologist). Soon after diagnosis, you’ll also likely meet with a diabetes educator and a registered dietitian to get more information on managing your diabetes.

Here’s some information to help you get ready for your appointment and to know what to expect.

What you can do

Be aware of any pre-appointment restrictions. When you make the appointment, ask if you need to do anything in advance. This will likely include restricting your diet, such as for a fasting blood sugar test.
Write down any symptoms you’re experiencing, including any that may seem unrelated.
Write down key personal information, including major stresses or recent life changes. If you’re monitoring your glucose values at home, bring a record of the glucose results, detailing the dates and times of testing.
Make a list of any allergies you have and all medications, vitamins and supplements you’re taking.
Record your family medical history. Be sure to note any relatives who have had diabetes, heart attacks or strokes.
Bring a family member or friend, if possible. Someone who accompanies you can help you remember information you need.
Write down questions to ask your provider. Ask about aspects of your diabetes management you’re unclear about.
Be aware if you need any prescription refills. Your provider can renew your prescriptions while you’re there.

Preparing a list of questions can help you make the most of your time with your provider. For diabetes, some questions to ask include:

Are the symptoms I’m having related to diabetes or something else?
Do I need any tests?
What else can I do to protect my health?
What are other options to manage my diabetes?
I have other health conditions. How can I best manage these conditions together?
Are there restrictions I need to follow?
Should I see another specialist, such as a dietitian or diabetes educator?
Is there a generic alternative to the medicine you’re prescribing?
Are there brochures or other printed material I can take with me? What websites do you recommend?

What to expect from your doctor

Your provider is likely to ask you many questions, such as:

Can you describe your symptoms?
Do you have symptoms all the time, or do they come and go?
How severe are your symptoms?
Do you have a family history of preeclampsia or diabetes?
Tell me about your diet.
Do you exercise? What type and how much?

By Mayo Clinic Staff

Diabetes care at Mayo Clinic

Request an appointment

Symptoms & causes
Doctors & departments

March 27, 2024

Ferri FF. Diabetes mellitus. In: Ferri’s Clinical Advisor 2022. Elsevier; 2022. https://www.clinicalkey.com. Accessed May 7, 2022.
Classification and diagnosis of diabetes: Standards of medical care in diabetes — 2022. Diabetes Care. 2022; doi:10.2337/dc22-S002.
Papadakis MA, et al., eds. Diabetes mellitus. In: Current Medical Diagnosis & Treatment 2022. 61st ed. McGraw Hill; 2022. https://accessmedicine.mhmedical.com. Accessed May 4, 2022.
Diabetes risk factors. Centers for Disease Control and Prevention. https://www.cdc.gov/diabetes/basics/risk-factors.html. Accessed June 2, 2022.
Cunningham FG, et al. Diabetes mellitus. In: Williams Obstetrics. 25th ed. McGraw-Hill Education; 2018. https://accessmedicine.mhmedical.com. Accessed June 2, 2022.
Diabetes and DKA (ketoacidosis). American Diabetes Association. https://www.diabetes.org/diabetes/dka-ketoacidosis-ketones. Accessed May 4, 2022.
Diabetes Canada Clinical Practice Guidelines Expert Committee. Complementary and alternative medicine for diabetes. Canadian Journal of Diabetes. 2018; doi:10.1016/j.jcjd.2017.10.023.
Nimmagadda R. Allscripts EPSi. Mayo Clinic. June 16, 2022.
Jameson JL, et al., eds. Diabetes mellitus: Diagnosis, classification and pathophysiology. In: Harrison’s Principles of Internal Medicine. 20th ed. McGraw-Hill Education; 2018. https://accessmedicine.mhmedical.com. Accessed June 2, 2022.
Pharmacologic approaches to glycemic treatment: Standards of medical care in diabetes — 2022. Diabetes Care. 2022; doi:10.2337/dc22-S009.
Facilitating behavior change and well-being to improve health outcomes: Standards of medical care in diabetes — 2022. Diabetes Care. 2022; doi:10.2337/dc22-S005.
AskMayoExpert. Type 1 diabetes mellitus. Mayo Clinic; 2021.
Glycemic targets: Standards of Medical Care in diabetes — 2022. Diabetes Care. 2022; doi:10.2337/dc22-S012.
Comprehensive medical evaluation and assessment of comorbidities: Standards of Medical Care in Diabetes — 2022. Diabetes Care. 2022; doi:10.2337/dc22-S004.
Prevention or delay of type 2 diabetes and associated comorbidities: Standards of Medical Care in diabetes — 2022. Diabetes Care. 2022; doi:10.2337/dc22-S003.
Obesity and weight management for the prevention and treatment of type 2 diabetes: Standards of Medical Care in Diabetes — 2022. Diabetes Care. 2022; doi:10.2337/dc22-S008.
Diabetes technology. Standards of Medical Care in Diabetes — 2022. 2022; doi:10.2337/dc22-S007.