1. Hba1c for diagnosis
Dr Karen Adamson

2. What is HbA1c?
• Glucose binds irreversibly to haemoglobin in red blood cells, forming HbA1c
• The higher the glucose, the higher the HbA1c
• HbA1c reflects the prevailing blood glucose over the preceding 2-3 months

3. Why Measure HbA1c?
• Serial measures show how an individual’s glucose control, and thus risk of complications, change in response to alterations in management
• Measure 2-6 monthly
• Set individual target levels

6. HbA1c as an Indicator of Glycaemic Control

7. Available Measures of Glycaemic Control
Fasting Plasma Glucose (FPG)*
Preferred test for diagnosis (mmol/l or mg/dL)
Snapshot of glycaemia
Oral Glucose Tolerance Test (OGTT)
Response to glucose challenge, can be used to diagnose disease
HbA1c (Glycated Haemoglobin)
Long-term measurement of glycaemic control (~3 months)
Postprandial Glucose (PPG)
Glucose level after eating (mmol/l or mg/dL)**
Random Blood Glucose (RBG)
Measures blood sugar at any point in time, normal levels not defined
Continuous Glucose Monitoring (CGM)
Assesses how blood glucose levels react to insulin, exercise and meals
There are several measures for glycaemic control.
Fasting Plasma Glucose (FPG)
Oral Glucose Tolerance Test (OGTT)
HbA1c (Glycosylated Haemoglobin)
Postprandial Glucose (PPG)
Random Blood Glucose (RBG)
Continuous Glucose Monitoring (CGM)
*measured after at least 8 hours of fasting; **measured 1- 2 hours after eating

8. Not suitable for HbA1C Rapid onset of diabetes
Suspected T1DM – see symptomatic patient flowchart
Drug-induced: steroids, anti-psychotics, immunosuppressants – a fasting glucose may not be sufficient. Seek advice from diabetes team.
Pancreatic disease. Seek advice from diabetes team.
Pregnancy – HbA1C reduced in pregnancy. Gestational diabetes should be diagnosed by OGTT. N.B. OGTT diagnostic criteria are lower than for the general population.
Conditions affecting Hb turnover / HbA1C assay
Haemoglobinopathy
Haemolytic anaemia
Severe blood loss, Blood transfusion
Splenomegaly / Splenectomy
Renal dialysis +/- erythropoitein
Anti-retrovirals, ribavarin, dapsone

9. + = DIABETES Diagnosis of diabetes mellitus in symptomatic patients
Thirst, polyuria
Unexpected weight loss
Symptomatic patient
Recurrent infection
Blurring of vision
Discoloured/ulcerated feet +
random glucose
≥11.1 mmol/L or
fasting glucose
≥7.0 mmol/L =
DIABETES
Mild symptoms
Severe symptoms
?ketotic
vomiting / dehydration
URGENT
HOSPITAL
ADMISSION
Full
assessment
& initiate
management of Type 2 Diabetes
young age
ketonuria
(or ketonaemia*) OR
URGENT
discussion with diabetes team
(may need insulin therapy)
*ketones can be measured on some POC glucometers

10. All glucose measurements used for diagnosis must be laboratory samples
Diagnosis of diabetes mellitus in asymptomatic patients
not diabetic
(repeat on
separate day)
≤6.0 mmol/L
random
glucose
≥11.1 mmol/L
repeat
fasting
glucose
high risk
Consider
HbA1C
6.1 – 6.9
mmol/L
fasting
glucose
INITIAL
lab
glucose
≥7.0 mmol/L
diabetes
≥7.0
mmol/L
(random OR
fasting)
7.8 – 11.0 mmol/L
6.1 – 6.9 mmol/L
random
glucose
fasting
suitable for HbA1C? *
YES NO
(repeat blood test on a separate day)
HbA1C
OGTT
not diabetic
high risk
not diabetic
high risk
diabetes
diabetes
≤41
mmol/mol
42 – 47
mmol/mol
≥48
mmol/mol
fasting
glucose
≤6.0
6.1 – 6.9
≥ 7.0
mmol/L
AND OR OR
All glucose measurements used for diagnosis must be laboratory samples
2-hr
glucose
≤7.7
7.8 – 11.0
≥ 11.1
mmol/L