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How to diagnose type 2 diabetes

by Debra Manzella, RN
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Diagnosing type 2 diabetes requires a series of laboratory tests that look for markers of elevated blood sugar levels. Such testing is necessary because type 2 diabetes may or may not have noticeable symptoms, and symptoms may intersect with other diseases.

Diagnosis is often made during an annual physical or physical exam. Your health care provider may administer a hemoglobin A1C test, fasting blood sugar (FBS) test, or oral glucose tolerance test (OGTT) as part of your routine screening to check your blood sugar levels and determine if you have diabetes. may be instructed.

Alex Dos Diaz / Very Well

Self-check/home inspection

More than 37.3 million Americans, or approximately 11% of the population, have diabetes, according to the most recent data available from the Centers for Disease Control and Prevention (CDC).

Additionally, 96 million American adults, or approximately 38% of the population, have prediabetes. Despite increased awareness efforts, many people with diabetes or pre-diabetes remain unaware of their condition.

Diabetes symptoms can be difficult to identify, but there are some signs that frequently coincide with high blood sugar and may indicate diabetes:

  • Frequent urination
  • feel thirsty frequently
  • excessive hunger
  • extreme fatigue
  • My nerves tingle
  • blurred vision
  • Cuts and bruises that heal slowly

Elevated blood sugar levels can lead to diabetes-related skin diseases. In particular, there are cases where:

  • skin tag: A small, harmless polyp-like tumor that often appears on the eyelids, neck, and armpits.
  • acanthosis nigricans: Dark, velvety patches of skin in skin creases on the back of the neck, armpits, elbow creases, hands, knees, groin area, etc.

Both conditions are thought to be related to insulin resistance.

If you think you may have diabetes, it is important to talk to your health care provider to get a confirmed diagnosis. Do not try to diagnose yourself using commercially available testing devices such as blood sugar monitors.

lab and testing

Regular screening for type 2 diabetes is recommended for everyone every 3 years starting at age 35, but more frequently if symptoms develop or your risk changes (such as weight gain). Masu. A health care provider may also recommend screening for obese or overweight adults who have one or more of the following known diabetes risk factors:

  • Family history of diabetes
  • HDL cholesterol level less than 35 mg/dL or triglyceride level greater than 250 mg/dL
  • History of gestational diabetes
  • history of heart disease
  • High blood pressure (140/90mmHg or higher)
  • Lack of exercise
  • Polycystic ovary syndrome (PCOS)
  • Symptoms related to insulin resistance

Type 2 diabetes is usually diagnosed with a hemoglobin A1C test, but if that test is not available or if you have a hemoglobin mutation that is difficult to test for, your health care provider may need to order another blood sugar test.

Because elevated blood sugar levels can be present early in both type 1 and type 2, your health care provider may also do additional tests to rule out type 1 diabetes.

Hemoglobin A1C test

A hemoglobin A1C test measures the percentage of glucose bound to hemoglobin, a protein that makes up part of red blood cells. This test shows your average blood sugar levels over the past two to three months. This is the approximate lifespan of a red blood cell. One advantage of this test is that it does not require fasting.

A1C results diagnosis
Less than 5.7% usually
5.7%~6.4% prediabetes
6.5% or more Diabetes

Some people of African, Mediterranean, or Southeast Asian descent may have genetic variations in their hemoglobin that can give them falsely high or falsely low results.

Random plasma glucose test (RPG)

A random blood sugar test checks your blood sugar levels to get a snapshot of your blood sugar status, regardless of when you last ate. This test is usually performed when a medical professional wants to check your blood sugar levels without having to wait for a fast, so it can be performed at any time.

RPG results diagnosis
Less than 200mg/dL usually
200mg/dL or more Diabetes

Although this test can be used to diagnose diabetes, it is not usually used to diagnose prediabetes.

Fasting plasma glucose (FPG)

The FPG test measures fasting blood sugar levels at a given point in time. A fasting test means that you do not eat for 8 to 10 hours before your blood is drawn. Most health care providers recommend getting tested first thing in the morning after an overnight fast.

FPG results diagnosis
99mg/dL or less usually
100mg/dL~125mg/dL prediabetes
126mg/dL or more Diabetes

Fasting blood sugar levels above 126 mg/dL indicate type 2 diabetes. Your health care provider may repeat a fasting blood glucose test twice to confirm the diagnosis.

Oral glucose tolerance test (OGTT)

OGTT is a glucose tolerance test. Fasting blood sugar levels are usually measured first to establish baseline levels. Next, you will be given a drink containing 75 grams of glucose (sugar). Two hours later, another blood sample will be taken to check your blood sugar levels.

OGTT results diagnosis
139mg/dL or less usually
140mg/dL~199mg/dL prediabetes
200mg/dL or more Diabetes

If your blood sugar levels are above 200 mg/dl, you may be diagnosed with type 2 diabetes. Again, your healthcare provider will typically perform this test on two different occasions before a definitive diagnosis is made.

Differential diagnosis

In addition to type 2 diabetes, several other conditions may be involved and can cause similar symptoms and, in some cases, show elevated blood sugar levels in blood tests.


Insulin resistance, or glucose intolerance, can affect the way your body processes and metabolizes glucose, but you may not be in the midst of full-blown type 2 diabetes yet. If you have prediabetes, your health care provider can help you develop a treatment plan to make lifestyle changes to prevent the disease from progressing.

Type 1 diabetes or subclinical autoimmune diabetes in adults

Symptoms of type 1 diabetes are very similar to type 2 diabetes, but they tend to appear all at once over a short period of time. Blood tests may show elevated blood sugar levels even with standard testing, but health care professionals can test for specific antibodies to detect type 1 (latent autoimmune diabetes in adults, or LADA). You should be able to add additional tests to see if you have the disease (possible). and proteins in the blood.

metabolic syndrome

Elevated blood sugar levels are only one of the factors that cause metabolic syndrome, and are thought to be associated with insulin resistance. Diagnostic criteria for metabolic syndrome include three of the following five elements:

  • Waist circumference of at least 35 inches for women and at least 40 inches for men
  • Triglyceride levels of 150 mg/dL or higher
  • High-density lipoprotein (HDL) cholesterol less than 40 mg/dL
  • Blood pressure is 130/85mm/Hg or higher
  • Fasting blood sugar level exceeds 100mg/dL

Treatment of metabolic syndrome involves modifying many lifestyle factors such as diet, exercise, and stress, but risk factors are usually reduced through positive changes.


Mild hyperglycemia (high blood sugar levels) and symptoms such as fatigue, tingling, anxiety, and weight loss may be associated with hyperthyroidism, or overactivity of the thyroid gland and overproduction of thyroxine. Your health care provider may perform additional tests to ensure that your thyroid is functioning well before ruling out this diagnosis.

Discussion Guide for Type 2 Diabetes Healthcare Providers

Get a printable guide to help you ask the right questions for your next healthcare provider appointment.


If you’ve been diagnosed with diabetes, there are many things you can do to prevent it from getting worse, starting with losing weight. According to the American Diabetes Association, overweight and obese diabetics can benefit greatly by reducing just 5% of their total body weight. Losses of 15% or more are most effective. A person with prediabetes can prevent progression to diabetes by simply losing 7% to 10% of her body weight.

This doesn’t mean you need to drastically reduce your diet. Your health care team can help you create a weight loss plan that includes a healthy, satisfying diet as well as moderate exercise (such as brisk walking, swimming, or cycling). 30 minutes, 5 days a week), including medication, supplements, and stress management practices as needed. Although admittedly unwelcome in some ways, a diabetes diagnosis can bring about positive changes in health and well-being that might not otherwise be possible.


  • How is type 2 diabetes diagnosed?

    Type 2 diabetes is diagnosed by measuring blood sugar levels. If a health care provider suspects diabetes, the first step is usually a finger prick in the office for a test called a random blood sugar test, followed by a test to check her fasting blood sugar level and her A1c. Other blood tests will follow.

  • What symptoms suggest testing for diabetes?

    Frequent urination, frequent thirst, excessive hunger, extreme fatigue, tingling in the feet and hands, blurred vision, and slow healing of cuts and bruises are symptoms of diabetes that should be checked.

  • Who should be tested for diabetes?

    The American Diabetes Association recommends getting screened starting at age 35. If the results are normal, he should be screened every three years unless there are risk factors or health changes. People with risk factors such as a family history of type 2 diabetes, heart disease, high blood pressure, kidney disease, diabetes before pregnancy, obesity, and a sedentary lifestyle may be screened for diabetes at an earlier age or more often. It may be recommended that you undergo

  • How can I test for diabetes at home?

    If you have a family member or friend who has diabetes and has a blood glucose meter, you can also ask them to test their blood sugar levels using the device (make sure to use a new lancet). Alternatively, you can purchase it at your local pharmacy. If your reading is above 200, contact your health care provider to be tested for diabetes.

Verywell Health uses only high-quality sources, including peer-reviewed research, to support the facts in our articles. Read our editorial process to learn more about how we fact-check and maintain the accuracy, reliability, and authenticity of our content.

  1. Centers for Disease Control and Prevention. National Diabetes Statistics Report.

  2. Centers for Disease Control and Prevention. diabetes symptoms.

  3. American Diabetes Association. Diabetes and skin complications.

  4. American Diabetes Association Specialty Practice Committee. 2. Diagnosis and classification of diabetes: Diabetes treatment standards-2024. diabetes care. 2024;47(Supplement 1):S20-S42. doi:10.2337/dc24-S002

  5. National Institute of Diabetes and Digestive and Kidney Diseases. A1C test and race/ethnicity.

  6. Evert AB, Dennison M, Gardner CD, et al. Nutritional therapy for adults with diabetes or prediabetes: a consensus report. diabetes care. 2019;42(5):731-754. doi:10.2337/dci19-0014

  7. National Institutes of Health: National Institute of Diabetes and Digestive and Kidney Diseases. Diabetes symptoms and causes.

  8. Roberts CK, Hevener AL, Bernard RJ. Metabolic syndrome and insulin resistance: underlying causes and improvement through exercise training. Compr Physiol. 2013;3(1):1–58. doi:10.1002/cphy.c110062

  9. Chen RH, Chen HY, Man KM, et al. Thyroid disease increases risk of type 2 diabetes: a nationwide cohort study. medicine. 2019;98(20):e15631. doi:10.1097/MD.0000000000015631

Debra Manzella, RN

Debra Manzella, MS, RN is a corporate clinical educator at Catholic Health System in New York and has extensive experience in diabetes care.

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