How Is Diabetes Diagnosed?

Everyone knows of someone who knows diabetes. 

This is because of the wide prevalence of this condition. 

But have you ever thought about how those diagnoses happen? 

What kind of testing is involved in order to diagnose diabetes? 

We will discuss all this and more here.

What is diabetes?

If you have diabetes, your body cannot properly process and use glucose from the food you eat. There are several different types of diabetes. Each has its own different potential causes. 

However, the one thing they all share is that they have too much sugar in your bloodstream. Treatments include medications such as insulin or adopting a healthy lifestyle.

In diabetes, your body cannot take glucose into its cells and use it for energy. This then leads to extra sugar in your bloodstream. 

If your diabetes is out of control, this can then result in some serious consequences. This includes damage to your body’s organs and tissues. Diabetes can impact your heart, kidneys, eyes, and nerves.

Who should be tested for diabetes?

You should get testing for diabetes if you have symptoms of diabetes. You should also get tested if you have risk factors for diabetes. This is because the earlier you catch diabetes, the earlier you can begin treatment. This can help to lessen and prevent complications.

If a blood test shows that you have prediabetes, your health care provider can work with you on making lifestyle changes. These usually include weight loss, exercise, and healthy nutrition. These can help to prevent and delay the development of type 2 diabetes.

Type 1 diabetes 

Children and young adults with a family history of diabetes should get this test. Though rare, it is also possible that older adults develop type 1 diabetes. 

If you go to the hospital and end up in diabetes-related ketoacidosis, this is a sign that you should get tested for type 1 diabetes, even if you are an adult. Ketoacidosis is a dangerous complication that can occur in type 1 diabetes.

Type 2 diabetes

 You should be tested for type 2 diabetes if you meet any of the following criteria:

  • You are 45 or older
  • Age 19 to 44 and overweight
  • Age 19 to 44 and have one or more risk factors
  • Women who have had gestational diabetes
  • Children aged 10 to 18 and overweight with at least two risk factors for type 2 diabetes

Gestational diabetes 

All pregnant women are tested for gestational diabetes between weeks 24 and 28 of pregnancy. However, your obstetrician may test you earlier if you have other risk factors for gestational diabetes. For example, this may happen if you have had a diagnosis of diabetes before.

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How does a doctor diagnose diabetes?

Type 1

If your doctor suspects you have type 1 diabetes, they will collect blood and urine samples from you. At the lab, they will check your blood for autoantibodies. 

Autoantibodies are a sign that your body is attacking itself. These are present in type 1 diabetes because it is an autoimmune condition where the body attacks its pancreas cells.

They will check your urine for ketones. Ketones signify that your body is burning fat as its primary energy supply. This happens in diabetes.

Type 2

Health care providers usually diagnose type 2 diabetes using the hemoglobin a1c test. This is a blood test. It indicates your average blood sugar level over the past two to three months.

According to the 2010 American Diabetes Association criteria, a hemoglobin a1c less than seven percent among treated patients with diabetes patients is what we consider adequate glycemic control.

Type 2 diabetes is often asymptomatic. Often it is not recognized until a random blood glucose test is done.

Some in the health community state that it is best to screen blood glucose levels in obese individuals. They state that this is more effective for identifying undiagnosed type 2 diabetes than screening the general population. 

Gestational diabetes

There are two blood glucose tests if you are pregnant. A glucose challenge test is when you drink a sugary liquid. One hour later, they will check your glucose level. If this test shows a glucose level over 140 milliliters per decilitre, then an oral glucose tolerance test will follow.

Gestational diabetes is a glucose tolerance disorder during pregnancy. It is associated with increased fetal and maternal morbidity. It is also related to long-term complications in both mother and child.

If you are at increased risk for diabetes, then screening for type 2 diabetes at the first prenatal visit is recommended. 

Risk factors for gestational diabetes

Risk factors for diabetes include the following:

  • History of gestational diabetes
  • History of prediabetes
  • Malformation, stillbirth, successive miscarriages, or birth weight over 4500 grams in past pregnancies
  • Obesity
  • Metabolic syndrome
  • Age over 35 years
  • Vascular disease
  • Clinical symptoms of diabetes such as glucosuria
  • Ethnic groups with increased risk for gestational diabetes or type 2 diabetes, such as Arabian countries, south and southeast Asia, and Latin America

The oral glucose tolerance test is recommended between weeks 24 to 48 weeks of pregnancy in all pregnant women with previous non-pathological glucose metabolism. 

In high-risk women, it may be prudent to do the oral glucose tolerance test in the first trimester instead. A single increased value is all you need to diagnose gestational diabetes.

If you have had bariatric surgery, however, the oral glucose tolerance test is not a good option due to the risk of postprandial hypoglycemia (low blood sugar after a meal).

After delivering the baby, anyone diagnosed with gestational diabetes needs to be re-evaluated using a 75-gram oral glucose tolerance test. This happens four to twelve weeks postpartum to reclassify glucose tolerance. If glucose tolerance is normal, then it is re-tested every two years.

Screening for gestational diabetes

The global prevalence of gestational diabetes is steadily rising. Based on the International Diabetes Federation extrapolation, the global prevalence will soon be 16.2 percent.

An ideal screening test for gestational diabetes should be able to identify women with gestational diabetes. However, it should also be capable of identifying women with a high risk of developing gestational diabetes. There is a lack of consensus among health care professionals regarding screening methods worldwide for gestational diabetes.

Some organizations suggest screening for high-risk pregnant women. Others recommend screening all pregnant women. Others prefer to offer definitive testing without screening. 

On top of this, the glycemic thresholds are not standard either. Different guidelines have different glycemic thresholds for the diagnosis of gestational diabetes. Even the prevalence rates of gestational diabetes that you see are different based on the glucose thresholds used for both screening and definitive testing.

Different screening methods involve the 50-gram one-hour glucose challenge test, fasting plasma glucose, random plasma glucose, and hemoglobin a1c with different cut-offs. 


Your doctor will diagnose pre-diabetes with a blood test. This will be through either a fasting plasma glucose test or the hemoglobin a1c test. 

Fasting plasma glucose tests your blood after an eight-hour fast. This means you have not consumed anything other than water. Hemoglobin a1c looks at your average blood glucose level over the past two to three months.

Prediabetes is the subclinical impairment in fasting plasma glucose, impaired glucose tolerance, or both. Prediabetes is in between euglycemia (healthy blood sugar levels) and hyperglycemia that we see in type 2 diabetes.

Over the past few years, research has found a clear link between prediabetes and cardiovascular disease. Recent studies show that patients with prediabetes can have coronary artery disease and diastolic heart failure even before they progress to diabetes. 

This highlights the importance of identifying prediabetes so that you can take appropriate measures to optimize glycemic control.

Researchers suggest that individuals over the age of 40 years should get diabetes screenings with fasting plasma glucose and/or hemoglobin a1c. The same is true for individuals at high risk of diabetes.

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

Fasting glucose

Those with prediabetes will have a fasting glucose level between 100 and 125 milligrams per decilitre. Patients with diabetes will have a fasting glucose at 126 milligrams per deciliter or higher. 

Random glucose 

Patients with prediabetes have a random glucose level between 140 and 199 milligrams per decilitre. If you have diabetes, random glucose will be at 200 milligrams per deciliter or higher. 

Hemoglobin a1c

Hemoglobin a1c levels between 5.7 and 6.4 percent indicate prediabetes. Patients with diabetes will have a hemoglobin a1c of 6.5 percent or higher. 

Oral glucose tolerance test 

With an oral glucose tolerance test, patients with prediabetes will have results between 140 and 199. Those with diabetes will have levels at 200 or higher than this.

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What are the symptoms of undiagnosed diabetes? 

One of the symptoms of undiagnosed diabetes is what we call polydipsia. Polydipsia is the medical term for increased thirst. High blood sugar levels can cause increased thirst.

Polyuria is another symptom of undiagnosed diabetes. Polyuria means increased urination. When you have polyuria, you need to urinate more often both throughout the day and throughout the night.

Another symptom of undiagnosed diabetes is polyphagia. This is the medical term for increased hunger.


You should now have an understanding of whether you should get tested for diabetes or not. And you know the various forms of testing that doctors use to diagnose diabetes. This includes type 1, type 2, gestational, and prediabetes. 

You now know what those pesky numbers on those tests mean and the symptoms to look out for in the case of undiagnosed diabetes.

If you suspect you may have diabetes or fall into a high-risk category, be sure to visit your doctor so they can test you for diabetes.

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  1. Braga, T; Kraemer-Aguiar, LG; Docherty, NG & Le Roux, CW. (2019). Treating prediabetes: why and how should we do it?. Minerva Med. 110 (1), 52-61.
  2. Kautzky-Willer, A et al.. (2019). Gestational diabetes mellitus (Update 2019). Wien Klin Wochenschr. 131 (Suppl 1), 91-102.
  3. Khan, RM; Chua, ZJ; Tan, JC; Yang, Y; Liao, Z & Zhao, Y. (2019). From pre-diabetes to diabetes: Diagnosis, treatments and translational research. Medicina (Kaunas). 55 (9), 546.
  4. Khetan, AK & Rajagopalan. (2018). Prediabetes. Can J Cardiol. 34 (5), 615-23.
  5. Malone, JI & Hansen, VBC. (2019). Does obesity cause type 2 diabetes mellitus (T2DM)? Or is it the opposite?. Pediatr Diabetes. 20 (1), 5-9.
  6. Rett, K & Gottwald-Hostalek, U. (2019). Understanding prediabetes: definition, prevalence, burden and treatment options for an emerging disease. Curr Med Res Opin. 35 (9), 1529-34.
  7. Sert, UY & Ozgu-Erdinc, AS. (2021). Gestational diabetes mellitus screening and diagnosis. Adv Exp Med Biol. 1307 (1), 231-55.
  8. Wang, L et al.. (2017). Prevalence and ethnic pattern of diabetes and prediabetes in China in 2013. JAMA. 317 (24), 2515-23.
  9. Yuen, L; Wong, VW & Simmons, D. (2018). Ethnic disparities in gestational diabetes. Curr Diab Rep. 23 (18), 9.
  10. Zand, A; Ibrahim, K & Patham, B. (2018). Prediabetes: Why should we care?. Methodist Debakey Cardiovasc J. 14 (4), 289-97.

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