When to screen for diabetes?

Guidelines for Diabetes Screening

It is estimated that one-third of people with diabetes are unaware of their condition. “Sometimes there can be virtually no symptoms, and patients can have diabetes and not know it,” says Jay Cohen, MD, adult and pediatric endocrinologist and clinical assistant professor of the department of family medicine and the department of pharmacology at the University of Tennessee.

If you have diabetes, screening for early diagnosis is essential. “The earlier that you diagnose diabetes, the better chance you can decrease the risk of developing diabetes complications, treating it appropriately, and helping stay healthy,” says Dr. Cohen. This is why diabetes screening is so important, but who should get screened and how often is diabetes screening recommended?

Diabetes Screening Recommendations

Most diabetes screening recommendations focus on type 2 diabetes, since symptoms of type 1 diabetes often develop suddenly and the disease is usually diagnosed soon after symptoms appear. People with type 2 diabetes can go undiagnosed for three to four years or more, says Cohen, making screening an important tool for catching it.

The American Diabetes Association (ADA) recommends that adults age 45 and older get screened for type 2 diabetes every three years by their health care provider.

You may need earlier or more frequent diabetes screening if you are overweight and have one or more of the following risk factors:

  • Family history of diabetes (a parent or sibling with the disease)
  • Sedentary lifestyle
  • African-American, Hispanic-American, Native-American, Asian-American, or Pacific Islander ancestry
  • History of blood glucose problems
  • History of gestational diabetes or a baby weighing over nine pounds
  • High blood pressure
  • Cholesterol problems
  • Polycystic ovary syndrome
  • History of vascular disease

The diabetes screening recommendations of other major health organizations differ somewhat from the ADA guidelines. For instance, the American Association of Clinical Endocrinologists recommends that high-risk adults get screened annually beginning at age 30.

Regardless of the organization, however, the message is generally the same: At some point, adults should begin getting regularly screened for type 2 diabetes, especially if they are at high risk of developing the disease.

Diabetes Screening in Children

Type 2 diabetes used to be considered an adult disease, but since overweight and obesity are on the rise in children, so is the prevalence of type 2 diabetes. Because of that, the ADA recommends that overweight children who also have two or more of the following risk factors undergo diabetes screening:

  • A family history of diabetes in a parent, sibling, aunt, uncle, or grandparent
  • Native-American, African-American, Hispanic-American, Asian-American, or Pacific Islander ancestry
  • Symptoms of insulin resistance
  • Conditions associated with insulin resistance, such as acanthosis nigricans (a skin pigment disorder), high blood pressure, cholesterol problems, and polycystic ovary syndrome

What Diabetes Screening Involves

There are two simple tests used in diabetes screening:

  • The fasting plasma glucose test involves checking the level of glucose in your blood while you are fasting. If your blood glucose level is higher than 125 mg/dL, you will need to be retested at another time to confirm a diabetes diagnosis.
  • The oral glucose tolerance test (OGTT) involves drinking a sugary solution two hours before you have your blood drawn. If your test results are 200 mg/dL or higher, you will need to have a repeat test another day to confirm that you have diabetes.

Talk with your doctor about the diabetes screening schedule best for you. If you do develop diabetes, early detection can be an important way to protect your health and prevent future complications.

Diabetes screening: Which patients, what tests, and how often?

Dr. Keenan is associate professor, department of medicine, University of California, Davis.

Principal Source: U.S. Preventive Services Task Force. Screening for type 2 diabetes mellitus in adults: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2008;148(11):846-854.—Discussant: Craig R. Keenan, MD

Practice Points

  • Screen annually for type 2 diabetes mellitus (T2DM), prediabetes, weight gain, and lipid abnormalities in all patients taking atypical antipsychotics.
  • Screen annually psychiatric patients age ≥30 who do not take atypicals for T2DM and prediabetes.
  • For patients age <30, regularly review your patients’ risk factors for diabetes to determine whom to screen for T2DM or prediabetes.
  • Screening is done most simply by ordering a fasting plasma glucose test.

Psychiatric patients—especially those with schizophrenia or taking atypical antipsychotics—are at risk for developing type 2 diabetes mellitus (T2DM) and prediabetes conditions. T2DM can be present for years without significant symptoms and even asymptomatic conditions increase the risk of cardiovascular, renal, retinal, and neurologic complications.

Despite a need for T2DM screening and treatment, expert guidelines disagree on who and how to screen (Table 1). Although testing patients who have diabetes symptoms—including polyuria, polydipsia, and weight loss—is indicated, some medical groups advocate screening asymptomatic persons for T2DM.

Screening recommendations

Consensus guidelines. In 2004, the American Diabetes Association (ADA), American Psychiatric Association (APA), American Association of Clinical Endocrinologists (AACE), and North American Association for the Study of Obesity (NAASO) created consensus guidelines for screening psychiatric patients receiving atypical antipsychotics. In addition to diabetes risk, psychiatric patients are at higher risk for metabolic syndrome, dyslipidemia, obesity, and hypertension.1 The ADA, APA, AACE, and NAASO recommend regularly screening for weight gain and dyslipidemia, obtaining baseline values of fasting plasma glucose (FPG), rechecking FPG after 3 months, and then screening annually for diabetes or prediabetes. For patients with risk factors for diabetes and those who develop diabetes or prediabetes while taking an atypical antipsychotic, consider an atypical with a lower risk of diabetes—specifically aripiprazole or ziprasidone.1 For psychiatric patients who do not take atypicals, there is no consensus on who and how to screen for T2DM.

The U.S. Preventive Services Task Force (USPSTF) recommends screening only adults with hypertension.2 Its review found insufficient evidence that early detection and treatment leads to improved clinical outcomes in asymptomatic adults.

The ADA recommends more liberal screening, including individuals age ≥45 or anyone age <45 who is overweight and has any other diabetes risk factors.3 The ADA admits that no trials show a benefit of screening asymptomatic patients but notes that the duration of glycemic burden predicts adverse outcomes and effective interventions for diabetes and prediabetes are available.

AACE guidelines recommend screening starting at age 30 if the patient has risk factors for T2DM. This is the only group that includes psychiatric illness as a risk factor.4

European Association for the Study of Diabetes (EASD) guidelines calculate a risk score based on common risk factors to determine who should be screened and recommend using the oral glucose tolerance test (OGTT) rather the FPG.5 The OGTT identifies more cases of diabetes and pre-diabetes but takes >2 hours to administer.

Table 1

General population screening recommendations for type 2 diabetes mellitus or prediabetes

Organization Year Whom to screen How to screen
U.S. Preventive Services Task Force (USPSTF) 2008 Asymptomatic adults with sustained blood pressure >135/80 mmHg (treated or untreated) FPG or OGTT every 3 years
American Diabetes Association (ADA) 2009 All adults age ≥45
Adults of any age with BMI >25 kg/m2 and ≥1 risk factors for diabetes (Table 2)
FPG or 2-hour OGTT every 3 years or more frequently, depending on initial results and risks
American Association of Clinical Endocrinologists (AACE) 2007 All adults age ≥30 with risk factors for diabetes (Table 2) FPG or 2-hour OGTT (frequency not specified)
European Association for the Study of Diabetes (EASD) and European Society of Cardiology (ESC) 2007 All adults with elevated risk score* OGTT (frequency not indicated)
FPG: fasting plasma glucose; OGTT: oral glucose tolerance test (75 gm glucose load); BMI: body mass index
*Risk scoring tool available at www.diabetes.fi/english/risktest


Despite a lack evidence showing benefit to the screened population, treating diabetes and its comorbidities improves outcomes, and the potential risks of therapy are low. Therefore, it seems reasonable to screen more patients than the USPSTF recommends.

Using the EASD risk score is intriguing, but difficult to implement in a busy practice. Therefore, I recommend following the AACE guidelines, which recognize psychiatric illness as a risk factor, for screening psychiatric patients who are not receiving atypicals.

Annually screen psychiatric patients age ≥30, especially those with schizophrenia or affective disorders. I also follow the ADA guidelines and screen overweight adults age ≤30 if they have any of the other risk factors listed in Table 2. The most common risk factors seen in practice are being a member of a high-risk ethnic group, hypertension, lipid abnormalities, and cardiovascular disease. For overweight adults without other risk factors, I start screening at age 30.

Diabetes Tests & Diagnosis

In this section:

  • Who should be tested for diabetes?
  • Type 1 diabetes
  • Type 2 diabetes
  • Gestational diabetes
  • What tests are used to diagnose diabetes and prediabetes?
  • What tests are used to diagnose gestational diabetes?
  • What test numbers tell me if I have diabetes or prediabetes?
  • Which tests help my health care professional know what kind of diabetes I have?

Your health care professional can diagnose diabetes, prediabetes, and gestational diabetes through blood tests. The blood tests show if your blood glucose, also called blood sugar, is too high.

Do not try to diagnose yourself if you think you might have diabetes. Testing equipment that you can buy over the counter, such as a blood glucose meter, cannot diagnose diabetes.

Who should be tested for diabetes?

Anyone who has symptoms of diabetes should be tested for the disease. Some people will not have any symptoms but may have risk factors for diabetes and need to be tested. Testing allows health care professionals to find diabetes sooner and work with their patients to manage diabetes and prevent complications.

Testing also allows health care professionals to find prediabetes. Making lifestyle changes to lose a modest amount of weight if you are overweight may help you delay or prevent type 2 diabetes.

Blood tests help health care professionals diagnose diabetes and prediabetes.

Type 1 diabetes

Most often, testing for type 1 diabetes occurs in people with diabetes symptoms. Doctors usually diagnose type 1 diabetes in children and young adults. Because type 1 diabetes can run in families, a study called TrialNet offers free testing to family members of people with the disease, even if they don’t have symptoms.

Type 2 diabetes

Experts recommend routine testing for type 2 diabetes if you

  • are age 45 or older
  • are between the ages of 19 and 44, are overweight or obese, and have one or more other diabetes risk factors
  • are a woman who had gestational diabetes1

Medicare covers the cost of diabetes tests for people with certain risk factors for diabetes. If you have Medicare, find out if you qualify for coverage. If you have different insurance, ask your insurance company if it covers diabetes tests.

Though type 2 diabetes most often develops in adults, children also can develop type 2 diabetes. Experts recommend testing children between the ages of 10 and 18 who are overweight or obese and have at least two other risk factors for developing diabetes.1

  • low birthweight
  • a mother who had diabetes while pregnant with them
  • any risk factor mentioned in Risk Factors for Type 2 Diabetes

Gestational diabetes

All pregnant women who do not have a prior diabetes diagnosis should be tested for gestational diabetes. If you are pregnant, you will take a glucose challenge test between 24 and 28 weeks of pregnancy.1

What tests are used to diagnose diabetes and prediabetes?

Health care professionals most often use the fasting plasma glucose (FPG) test or the A1C test to diagnose diabetes. In some cases, they may use a random plasma glucose (RPG) test.

Fasting plasma glucose (FPG) test

The FPG blood test measures your blood glucose level at a single point in time. For the most reliable results, it is best to have this test in the morning, after you fast for at least 8 hours. Fasting means having nothing to eat or drink except sips of water.

A1C test

The A1C test is a blood test that provides your average levels of blood glucose over the past 3 months. Other names for the A1C test are hemoglobin A1C, HbA1C, glycated hemoglobin, and glycosylated hemoglobin test. You can eat and drink before this test. When it comes to using the A1C to diagnose diabetes, your doctor will consider factors such as your age and whether you have anemia or another problem with your blood.1 The A1C test is not accurate in people with anemia.

If you’re of African, Mediterranean, or Southeast Asian descent, your A1C test results may be falsely high or low. Your health care professional may need to order a different type of A1C test.

Your health care professional will report your A1C test result as a percentage, such as an A1C of 7 percent. The higher the percentage, the higher your average blood glucose levels.

People with diabetes also use information from the A1C test to help manage their diabetes.

Random plasma glucose (RPG) test

Sometimes health care professionals use the RPG test to diagnose diabetes when diabetes symptoms are present and they do not want to wait until you have fasted. You do not need to fast overnight for the RPG test. You may have this blood test at any time.

What tests are used to diagnose gestational diabetes?

Pregnant women may have the glucose challenge test, the oral glucose tolerance test, or both. These tests show how well your body handles glucose.

Glucose challenge test

If you are pregnant and a health care professional is checking you for gestational diabetes, you may first receive the glucose challenge test. Another name for this test is the glucose screening test. In this test, a health care professional will draw your blood 1 hour after you drink a sweet liquid containing glucose. You do not need to fast for this test. If your blood glucose is too high—135 to 140 or more—you may need to return for an oral glucose tolerance test while fasting.

Oral glucose tolerance test (OGTT)

The OGTT measures blood glucose after you fast for at least 8 hours. First, a health care professional will draw your blood. Then you will drink the liquid containing glucose. For diagnosing gestational diabetes, you will need your blood drawn every hour for 2 to 3 hours.

High blood glucose levels at any two or more blood test times during the OGTT—fasting, 1 hour, 2 hours, or 3 hours—mean you have gestational diabetes. Your health care team will explain what your OGTT results mean.

Health care professionals also can use the OGTT to diagnose type 2 diabetes and prediabetes in people who are not pregnant. The OGTT helps health care professionals detect type 2 diabetes and prediabetes better than the FPG test. However, the OGTT is a more expensive test and is not as easy to give. To diagnose type 2 diabetes and prediabetes, a health care professional will need to draw your blood 1 hour after you drink the liquid containing glucose and again after 2 hours.

What test numbers tell me if I have diabetes or prediabetes?

Each test to detect diabetes and prediabetes uses a different measurement. Usually, the same test method needs to be repeated on a second day to diagnose diabetes. Your doctor may also use a second test method to confirm that you have diabetes.

The following table helps you understand what your test numbers mean if you are not pregnant.

Diagnosis A1C (percent) Fasting plasma glucose (FPG)a Oral glucose tolerance test (OGTT)ab Random plasma glucose test (RPG)a
Normal below 5.7 99 or below 139 or below
Prediabetes 5.7 to 6.4 100 to 125 140 to 199
Diabetes 6.5 or above 126 or above 200 or above 200 or above

Which tests help my health care professional know what kind of diabetes I have?

Even though the tests described here can confirm that you have diabetes, they can’t identify what type you have. Sometimes health care professionals are unsure if diabetes is type 1 or type 2. A rare type of diabetes that can occur in babies, called monogenic diabetes, can also be mistaken for type 1 diabetes. Treatment depends on the type of diabetes, so knowing which type you have is important.

To find out if your diabetes is type 1, your health care professional may look for certain autoantibodies. Autoantibodies are antibodies that mistakenly attack your healthy tissues and cells. The presence of one or more of several types of autoantibodies specific to diabetes is common in type 1 diabetes, but not in type 2 or monogenic diabetes. A health care professional will have to draw your blood for this test.

If you had diabetes while you were pregnant, you should get tested no later than 12 weeks after your baby is born to see if you have type 2 diabetes.

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Diabetes is a group of conditions in which a person’s body can’t maintain healthy levels of sugar (glucose) in their blood. High blood sugar levels can cause health problems over time.

Someone can have diabetes without experiencing any symptoms. Your doctor may ask you to get tested if you are at risk of diabetes.

Am I at risk of diabetes?

You can ask your doctor about your risk for diabetes. You can also estimate your risk of getting type 2 diabetes by using the Australian Type 2 Diabetes Risk Assessment Tool (AUSDRISK). This is a simple way for you to check your risk.

You may be at increased risk of type 2 diabetes if you:

  • are over 40
  • have a family member with type 2 diabetes
  • are from an Aboriginal or Torres Strait Islander background
  • were born in Asia
  • are not physically active

Who should have a diabetes test?

You should have a diabetes test if you are at a high risk of type 2 diabetes. An AUSDRISK score of 12 or more is considered high risk.

You may also be at high risk of diabetes if you:

  • have had a heart attack or stroke before
  • have had gestational diabetes (a type of diabetes that occurs during pregnancy)
  • have polycystic ovary syndrome
  • take medications to treat psychosis

You should have a diabetes test every year if you have pre-diabetes.

What happens during a diabetes test?

Diabetes is usually tested by using a blood glucose test. Normally, a blood sample is taken from your vein and sent to a pathology lab for analysis.

There are different types of blood test. You may be asked to fast overnight beforehand (fasting blood glucose test) or you may not need to prepare. You may be asked to take an oral glucose tolerance test. For this test, you are asked to fast, have a blood sample taken, then drink a sugary drink provided for you and have another blood sample taken 2 hours later.

What does a diabetes test cost?

If you have a Medicare card and your doctor orders the diabetes test for you, the test is usually bulk billed. That means there are no out-of-pocket costs to you. However, you can call the pathology lab to ask about costs.

How can I get tested?

Speak to your doctor about having your risk of diabetes assessed. If your doctor thinks you should be tested, they will usually fill in a pathology request form, which you take to a pathology collection centre to have the blood test.

What follow-up is involved?

You will usually need to see your doctor to get your test results. Ask your doctor when you should return for your next diabetes test. This will depend on your level of risk.

Prediabetes Screening: How and Why

Screening involves the testing of asymptomatic, high-risk individuals to assess whether they meet the criteria for either prediabetes or type 2 diabetes. Screening recommendations have been made by different groups, including the American Diabetes Association and the United States Preventive Services Task Force. Although these recommendations sometimes advise screening for slightly different groups of individuals, all of them advise the use of one or more blood tests to determine the degree of blood glucose elevation.

Screening for prediabetes and diabetes is more frequently done in health care settings than community settings. The process used to target and test patients may include a team approach, employing various health care professionals such as medical assistants, nurses, physicians, diabetes educators, or others. Electronic health records can alert health care team members about patients who should be targeted for diabetes screening, either during or between visits to the clinic. Health care providers in a variety of practice settings can consider use of standard ordering protocols for glucose testing, which may be approved by physicians up front but carried out by other team members when at-risk patients are identified. In addition, provider teams can look for opportunities to screen for prediabetes while managing a patient’s other conditions. For example, when screening for hyperlipidemia, a fasting glucose may easily be added to a standard fasting lipid test panel.

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