Screening for and Diagnosing Diabetes
Healthcare Provider Tool
Reset
Measure Fasting Plasma Glucose (FPG) and/or A1C and enter test results:
| mmol/L | % |
Or
Measure 75g Oral Glucose Tolerance Test (OGTT) and enter test results:
| mmol/L | mmol/L |
Not enough information is provided
Rescreen as recommended, every 3 years.
ERROR
Enter value for FPG and/or A1C; or OGTT only.
Normal
(Re)screen as recommended
At risk for prediabetes and type 2 diabetes
Rescreen more often
Prediabetes
Rescreen more often
Diabetes
Tests are discordant
The patient may have diabetes, suggest repeat A1C. If patient has symptoms of hyperglycemia, confirmatory / repeat test is not required, consider patient to have diabetes.
Tests are discordant
The patient may have diabetes, suggest repeat FPG. If patient has symptoms of hyperglycemia, confirmatory / repeat test is not required, consider patient to have diabetes.
Normal
IGT (prediabetes)
Possible diabetes
Confirmatory test required. If patient has symptoms of hyperglycemia, confirmatory / repeat test is not required, consider patient to have diabetes.
Diabetes
IFG (prediabetes)
IFG and IGT (prediabetes)
This test is normal
(Re)screen as recommended
This represents someone at risk
Consider A1C test, rescreen more often
This represents prediabetes
Consider A1C test, rescreen more often
This might represent diabetes
Requires second test for confirmation, consider repeat FPG and / or A1C test. If patient has symptoms of hyperglycemia, confirmatory / repeat test is not required, consider patient to have diabetes.
This represents someone at risk
Consider FPG test, rescreen more often
This represents prediabetes
Consider FPG test, rescreen more often
This might represent diabetes
Requires second test for confirmation, consider repeat A1C and / or FPG. If patient has symptoms of hyperglycemia, confirmatory / repeat test is not required, consider patient to have diabetes.
Review Clinical Practice Guidelines' Chapter 4: Screening for Type 1 and Type 2 Diabetes for more detailed information.
- Age ≥40 years
- First-degree relative with type 2 diabetes
- Member of high-risk population (e.g., African, Arab, Asian, Hispanic, Indigenous or South Asian descent, low socioeconomic status)
- History of prediabetes (lGT, lFG or A1C 6.0–6.4%)*
- History of GDM
- History of delivery of a macrosomic infant
- Presence of end organ damage associated with diabetes:
- Microvascular (retinopathy, neuropathy, nephropathy)
- CV (coronary, cerebrovascular, peripheral)
- Presence of vascular risk factors:
- HDL-C <1.0 mmol/L in males, <1.3 mmol/L in females*
- TG ≥1.7 mmol/L*
- Hypertension*
- Overweight*
- Abdominal obesity*
- Smoking
- Presence of associated diseases:
- History of pancreatitis
- Polycystic ovary syndrome*
- Acanthosis nigricans*
- Hyperuricemia/gout
- Non-alcoholic steatohepatitis
- Psychiatric disorders (bipolar disorder, depression, schizophrenia†)
- HlV infection‡
- Obstructive sleep apnea§
- Cystic fibrosis
- Use of drugs associated with diabetes:
- Glucocorticoids
- Atypical antipsychotics
- Statins
- Highly active antiretroviral therapy‡
- Anti-rejection drugs
- Other (see Appendix 1)
- Other secondary causes (see Appendix 1)
AIC, glycated hemoglobin; CV, cardiovascular; GDM, gestational diabetes; HDL-C, high density lipoprotein cholesterol; HIV, human immunodeficiency virus-1; IFG, impaired fasting glucose; IGT, impaired glucose tolerance.
- Screen every 3 years in individuals ≥40 years of age
- Screen every 3 years in individuals at high risk according to a risk calculator
- Screen earlier and/or more frequently (every 6 to 12 months) in people with additional risk factors for diabetes (see below)
- Screen earlier and/or more frequently in people at very high risk according to a risk calculator
Conditions that lead to misleading A1C include: hemoglobinopathies, hemolytic anemia, iron deficiency, severe renal or liver disease. Link to Table 1, Monitoring for Glycemic Control.
- Validated Assay: A1C must be measured using a validated assay standardized to the National Glycohemoglobin Standardization Program-Diabetes Control and Complications Trial reference.
- Ethnicity: Studies indicate that African Americans, American Indians, Hispanics and Asians have A1C values that are up to 0.4% higher than those of Caucasian patients at similar levels of glycemia (17,18). Research is required to determine if A1C levels differ in African Canadians or Canadian First Nations.
- Age: A1C values are affected by age, rising by up to 0.1% per decade of life (20,21). More studies may help to determine if age- or ethnic-specific adjusted A1C thresholds are required for diabetes diagnosis.
- Special Populations: A1C is not recommended for diagnostic purposes in children, adolescents, pregnant women or those with suspected type 1 diabetes.
See Individualizing Your Patient’s A1C target, Chapter 9: Monitoring Glycemic Control, Table 1
Chapter 4: Figure 1. Screening and diagnosis algorithm for type 2 diabetes.
| Chapter 3: Table 5 Diagnosis of prediabetes |
||
|---|---|---|
| 2hPG, 2-hour plasma glucose; AlC, glycated hemoglobin; FPG, fasting plasma glucose; IFG, impaired fasting glucose; IGT, impaired glucose tolerance; OGTT, oral glucose tolerance test. | ||
| Test | Result | Prediabetes category |
| FPG (mmol/L) | 6.1–6.9 | IFG |
| 2hPG in a 75 g OGTT (mmol/L) | 7.8–11.0 | IGT |
| A1C (%) | 6.0–6.4 | Prediabetes |
| Parameter | Advantages | Disadvantages |
|---|---|---|
| 2hPG, 2-hour plasma glucose; A1C, glycated hemoglobin; CVD, cardiovascular disease; FPG, fasting plasma glucose; OGTT, ral glucose tolerance test. | ||
| FPG |
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| 2hPG in a 75 g OGTT |
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| A1C |
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