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Diabetes Diagnostic Criteria and Screening

Understanding the screening and diagnosis of diabetes helps educators direct clients to physicians for assessment and treatment. Most educators may not formally diagnose diabetes within their scope of practice. However, understanding this information helps them explain diagnostic bloodwork and related co-morbidities. Educators also play an important role in helping clients build conviction to be screened and to follow-up on results.

Screening and Risk Factors 

Case: Use the Online Screening and Diagnosis Calculator above for this case. Agnes has an A1c of 6.2% and a fasting of 7.9 mmol/L. Does she have pre-diabetes, diabetes or is another confirmatory test required?

Diagnostic Criteria

 Diabetes and PreDiabetes Diagnostic Criteria

 Diagnosis is made if one or more values is exceeded and confirmed.* 

Value Normal Diabetes PreDiabetes
Fasting (mmol/L)  3.9 - 6.0 > 7.0  6.1 - 6.9
2 hr pc or
2 hr OGTT (mmol/L)
 4.4 - 7.7 > 11.1  7.8 - 11.0
A1c  < 6% usually >  6.5%  6.0 - 6.4%
 < 7.8 > 11.1  n/a
*A1c for use in adults with the absence of factors that affect A1c accuracy. If no symptomatic hyperglycemia, a confirmatory test is required. A random glucose in an asymptomatic individual should be confirmed with an alternate test. A confirmatory test is not required in the case of symptomatic hyperglycemia. IFG= Impaired fasting glucose; IGT= Impaired glucose tolerance; OGTT = oral glucose tolerance test. Source Diabetes Canada:  

Gestational Diabetes Diagnostic Criteria

 Diagnosis of GDM is made if one value or more is exceeded for either OGTT test.

Value (mmol/L) 50 gram OGTT Preferred 75 gram OGTT after 50 g test Alternative 75 gram OGTT (one test only)
Fasting    > 5.3  > 5.1
1 hr pc    > 11.1 diagnostic of GDM

If 7.8 - 11.0 proceed to preferred 75 OGTT test.
> 10.6 > 10.0
2 hr pc    > 9.0  > 8.5
Testing for all pregnant women between 24 and 28 weeks gestation, or at any stage of pregnancy if high risk for GDM.  Source: Diabetes Canada 

A Note on Conviction

Screening for diabetes sounds like a simple task to check off on a lab requisition. However, clients may be hesitant to get bloodwork completed, to return to the physician for results or to follow-up with management strategies if prediabetes or diabetes is diagnosed.

Fear can often guide people’s behavior, or lack of behavior. Assessing a client’s conviction to complete screening activities is crucial. Educators may need to build conviction by offering (with permission) information on the benefits of early diagnosis and management. More importantly, educators may need to relate these benefits to helping clients with their personal dreams and priorities. This requires caring questions to learn what is important in each client’s life.