There are various techniques to identify diabetes, which typically require confirmation through repeated testing. These tests are usually conducted in a medical facility. In cases where blood sugar levels are significantly elevated, or if classic symptoms are present in addition to a positive result, a second test may not be needed.
The A1C test, which does not require fasting, provides an average of blood sugar levels over a period of 2-3 months. Diabetes is confirmed with an A1C level of 6.5% or above.
Table
| Outcome | Hemoglobin A1C |
|---|
| Healthy | Less than 5.7% |
| At Risk | 5.7% to 6.4% |
| Unhealthy | 6.5% or higher |
Fasting Plasma Glucose (FPG)
During this test, fasting blood glucose levels are measured after an 8-hour fast. A diagnosis of diabetes is made if fasting glucose levels are 126 mg/dl or above.
Table
| Outcome | Levels of Glucose in Blood after Fasting |
|---|---|
| Healthy | below 100 mg/dL |
| Potential risk of diabetes | 100 to 125 mg/dL |
| Confirmed diabetes | 126 mg/dL or above |
It is important to note that fasting glucose levels can vary slightly between different laboratories and testing methods. Additionally, it is recommended to consult with a healthcare provider for further evaluation and interpretation of FPG results.
Diagnosing Diabetes with OGTT
OGTT involves testing blood sugar levels before and after drinking a sugary beverage. A diagnosis of diabetes is made when blood glucose levels reach 200 mg/dl or above after two hours.
Chart
| Outcome | Procedure for assessing glucose tolerance through the OGTT |
|---|
| Healthy | Below 140 mg/dL |
| Borderline | 140 to 199 mg/dL |
| High Risk | 200 mg/dL or above |
Random (also called Casual) Plasma Glucose Test
This test assesses blood glucose levels at any given time when severe diabetes symptoms are present. Diabetes is typically diagnosed when blood glucose levels reach 200 mg/dl or higher.
What is Prediabetes?
Prior to the onset of type 2 diabetes, individuals often experience prediabetes characterized by elevated glucose levels. This condition elevates the risk of developing type 2 diabetes as well as cardiovascular diseases.
Symptoms
Symptoms of prediabetes may not always be obvious, but some individuals may display symptoms or complications associated with diabetes. Prediabetes is usually detected during diabetes screenings, and it is advised for individuals with prediabetes to undergo regular screenings for type 2 diabetes.
Indicators of prediabetes include: A1C levels between 5.7–6.4%, Fasting glucose levels of 100–125 mg/dL, and OGTT two-hour glucose levels of 140–199 mg/dL.
Preventing Type 2 Diabetes
Prediabetes does not necessarily lead to the development of type 2 diabetes. Early intervention and lifestyle changes are key in reducing this risk. Weight loss and physical activity can significantly decrease the likelihood of developing type 2 diabetes.
Diagnosis of diabetes, prediabetes, and gestational diabetes is conducted through blood tests in a medical setting. Over-the-counter blood testing devices are not suitable for diagnosing diabetes.
It is important for individuals with prediabetes to make lifestyle changes such as maintaining a healthy diet, exercising regularly, and monitoring their blood sugar levels. By taking proactive steps, individuals can reduce their risk of developing type 2 diabetes and improve their overall health.
Who should be tested for diabetes?
Screening for diabetes is recommended for individuals exhibiting symptoms or those with risk factors. Most pregnant women should also undergo testing for gestational diabetes. Early detection plays a crucial role in managing diabetes and preventing complications.
Type 1 diabetes
Type 1 diabetes is typically diagnosed in children and young adults based on symptoms or the presence of diabetic ketoacidosis. There may be a genetic predisposition to type 1 diabetes, and free testing is available for relatives of individuals with this condition through TrialNet.
Type 2 diabetes
Regular screening for type 2 diabetes is advised for individuals with specific risk factors such as age, ethnicity, and a history of gestational diabetes. The Diabetes Risk Test by the American Diabetes Association helps in assessing the risk of developing type 2 diabetes.
Children can also develop type 2 diabetes, and it is recommended to screen overweight individuals with additional risk factors.
Gestational diabetes
Gestational diabetes testing is recommended for pregnant women between 24 and 28 weeks of pregnancy. Postpartum testing for type 2 diabetes is also encouraged.
What tests are used to diagnose diabetes?
Various tests are utilized in the diagnosis of diabetes and prediabetes based on symptoms, pregnancy, and other factors. These tests may include fasting plasma glucose, A1C, and random plasma glucose tests.
Fasting plasma glucose test
The fasting plasma glucose (FPG) test measures blood glucose levels after an 8-hour period of fasting. It is advisable to conduct this test in the morning on an empty stomach, with only water permitted.
A1C test
The A1C test provides a reflection of average blood glucose levels over the past 3 months and is not influenced by food consumption. Certain factors like pregnancy or blood disorders can affect the accuracy of the test.
Hemoglobin variants may impact the results of the A1C test, rendering it unreliable in such cases. Results are presented as a percentage.
Random plasma glucose test
The random plasma glucose test diagnoses diabetes without the need for fasting. It can be conducted at any time, particularly when symptoms are present.
Glucose challenge test
During pregnancy, the glucose challenge test, also known as the glucose screening test, may be administered to test for gestational diabetes. A blood sample is taken 1 hour after consuming a glucose-laden liquid. If the blood glucose level is elevated (135 mg/dL to 140 mg/dL or higher), an oral glucose tolerance test may be required after fasting.
Oral glucose tolerance test
The oral glucose tolerance test (OGTT) is used to detect type 2 diabetes, prediabetes, and gestational diabetes. This test is more complex and expensive compared to the FPG and glucose challenge tests.
Prior to the test, fasting for at least 8 hours is necessary. A blood sample is taken to measure glucose levels after fasting, followed by the consumption of a high-sugar beverage and another blood sample 2 hours later. Elevated blood glucose levels may indicate diabetes. For pregnant individuals, blood samples are taken every hour for 2 to 3 hours during the test.
What test results tell me if I have diabetes or prediabetes?
Each diabetes diagnostic test utilizes distinct measurements. A secondary test may be employed by your doctor to confirm a diabetes diagnosis.
The table illustrates the interpretation of test results for non-pregnant individuals. Different cutoffs may apply for pregnant women, hence consulting a healthcare professional for interpretation is advisable.
Test results for diagnosis of prediabetes and diabetes
| Diagnosis | A1C Level | Fasting Blood Sugar | Oral Glucose Tolerance Test* | Random Blood Sugar Test‡ |
|---|
| Status | A1C | Fasting Glucose | Oral Glucose Tolerance Test | Random Glucose Test |
| Normal | below 5.7% | 99 mg/dL or below | 139 mg/dL or below | N/A |
| Pre-diabetes | 5.7% to 6.4% | 100 to 125 mg/dL | 140 to 199 mg/dL | N/A |
| Diabetes | 6.5% or above | 126 mg/dL or above | 200 mg/dL or above | 200 mg/dL or above |
* Glucose intake should be measured 2 hours after consumption to determine diabetes. In case of symptoms, testing should be done as indicated by the American Diabetes Association.
Which tests help my doctor know what kind of diabetes I have?
The tests available can confirm the presence of diabetes but cannot differentiate between the types. Correct identification of the type is crucial as treatment depends on it.
Genetic testing
Genetic testing is effective in diagnosing most forms of monogenic diabetes caused by gene mutations. This type of diabetes is prevalent in certain age groups.
Autoantibodies
Individuals with diabetes may be tested for autoantibodies associated with type 1 diabetes, which are known to attack healthy tissues. A positive result indicates the presence of type 1 diabetes, and this test may also be conducted on individuals with a family history of the condition.
Reference
References:
– American Diabetes Association Professional Practice Committee. Standards of medical care in diabetes—2022. Diabetes Care. 2022;45(suppl 1):1–16.7
Information from the National Institute of Diabetes and Digestive and Kidney Diseases highlights the importance of confirming diabetes through laboratory testing.
Diabetes test: How to test for diabetes
Diagnosis of diabetes relies on laboratory results that are usually available within a few days. Prompt results are especially critical in hospital settings.
A finger prick test can indicate high blood sugar levels but is not sufficient for a definitive diagnosis. Blood tests are essential for confirmation.
A normal blood test may not show signs of diabetes but can indicate a risk for developing type 2 diabetes.
Signs and symptoms of diabetes
Diagnosis of diabetes can sometimes be challenging due to subtle symptoms. It is important to address concerns with a healthcare provider persistently.
In case of feeling unwell, seek immediate medical attention.
Testing for type 1 and type 2 diabetes
Diabetes diagnosis takes into consideration various factors such as onset, severity, weight, age, and family history. Test results can help predict the risk of type 2 diabetes.
Additional testing may be required to differentiate between type 1 and type 2 diabetes. Early signs of type 1 diabetes may necessitate assessment in a hospital setting.
Testing for the risk of type 1 diabetes involves identifying early markers that suggest potential future diagnosis. These markers indicate immune system attacks on the pancreas.
Blood tests used to diagnose diabetes
Healthcare providers will choose from a range of blood tests tailored to the individual’s symptoms for diabetes diagnosis.
Non fasting blood tests
HbA1c:
The HbA1c test assesses the average blood sugar levels over a few months. Results exceeding 48mmol/mol are indicative of diabetes. Routine blood tests with varying glucose levels can also diagnose diabetes. Random blood glucose test:
A random blood glucose test can identify diabetes through high glucose levels at any time. Definitive diagnosis requires confirmation through laboratory blood tests.
Fasting blood tests
Fasting blood sugar test:
The fasting blood sugar test measures blood glucose levels after an overnight fast. Results above 7mmol/l indicate diabetes.
Fasting is important for accurate results in diabetes diagnosis. Glucose tolerance test (GTT):
An Oral Glucose Tolerance Test checks how well the body processes sugar from food. It is also known as an OGTT and is used for diagnosing gestational diabetes.
The test consists of two parts: a fasting test to assess blood glucose levels and a sugary drink consumed to observe the body’s response. Another blood test is conducted two hours later. Results, indicating levels from both tests, are usually available within a few days.
If pregnant, gestational diabetes is diagnosed if fasting glucose is 5.6mmol/l+ (first test) and 2-hour glucose is 7.8mmol/l+ (second test).
For more information on gestational diabetes, click here.
Other information about testing and diagnosis
Urine tests cannot diagnose diabetes but can detect the presence of sugar in the urine without providing specific amounts or reasons for it.
Home diabetes testing kits do not provide a definitive diagnosis but indicate blood sugar levels at the time of testing.
Although an optician cannot diagnose diabetes, they can identify eye damage related to diabetic retinopathy.
Pharmacists offer screenings to assess the risk of type 2 diabetes, which serves as guidance rather than a diagnosis. Seek medical assistance if at risk, as blood tests for diabetes may be available for a fee.
Check your risk using our online tool to determine the likelihood of developing type 2 diabetes for free.
Diagnosed with diabetes – what next
Receiving a diabetes diagnosis can feel overwhelming. Adequate treatment and support are essential for effective management.
Bring a family member or friend to healthcare appointments and jot down any questions you may have.
Healthcare providers will discuss treatment options, lifestyle adjustments, dietary modifications, exercise plans, and recommendations regarding smoking and alcohol consumption to manage diabetes safely.
Our information – where to start
Start by exploring our basic information on diabetes and learn about maintaining a healthy diet with diabetes.
For children diagnosed with diabetes, seek support and resources. Use our helpline for assistance.
Save helpful pages, such as recipes, with Diabetes and Me. Watch informative video tips on the Learning Zone.
If you’re at risk of getting type 2 diabetes
Elevated blood sugar levels may suggest a future risk of type 2 diabetes, even in the absence of a current diabetes diagnosis.