{"id":17863,"date":"2024-01-10T16:12:09","date_gmt":"2024-01-10T16:12:09","guid":{"rendered":"https:\/\/apps.nhslothian.scot\/refhelp\/?page_id=17863"},"modified":"2026-04-15T11:31:15","modified_gmt":"2026-04-15T10:31:15","slug":"diabetes-diagnosis","status":"publish","type":"page","link":"https:\/\/apps.nhslothian.scot\/refhelp\/guidelines\/diabetes\/diabetes-diagnosis\/","title":{"rendered":"Diabetes Diagnosis"},"content":{"rendered":"\n

Supporting Information<\/h4>\n\n\n
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\"Diabetes
NHS Lothian<\/span><\/figcaption><\/figure>\n<\/div>\n\n\n

Diagnostic Criteria<\/strong><\/p>\n\n\n\n

Diabetes and pre-diabetes may be diagnosed by any of the following criteria:<\/p>\n\n\n\n

 <\/td>Diabetes<\/td>Pre-Diabetes<\/td>Normal<\/td><\/tr>
HbA1c (mmol\/mol)<\/td>\u2265 48<\/td>42-47<\/td>\u2264 41<\/td><\/tr>
Fasting glucose (mmol\/l)<\/td>\u2265 7.0<\/td>6.1-6.9<\/td>\u2264 6.0<\/td><\/tr>
2-hr glucose in OGTT (mmol\/l)<\/td>\u2265 11.1<\/td>7.8-11.0<\/td>\u2264 7.7<\/td><\/tr>
Random glucose (mmol\/l)<\/td>\u2265 11.1<\/td> <\/td> <\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Types of Diabetes<\/h4>\n\n\n\n

Diabetes mellitus has many different causes. It is very important that the full potential differential diagnosis is considered in all new presentations of diabetes. <\/p>\n\n\n\n

Type 1 Diabetes <\/em><\/em><\/p>\n\n\n\n

This results from an absolute deficiency of insulin due to autoimmune pancreatic beta-cell destruction. It more commonly presents acutely in young people, but can occur at any age.  A history of significant weight loss prior to diagnosis and the presence of ketones in the urine or blood are highly suggestive of type 1 diabetes. People with type 1 diabetes usually have detectable antibodies to GAD, IA-2 and\/or ZnT8. Type 1 diabetes can occur in any individual regardless of age, ethnicity or weight. Therefore, measurement of blood or urine ketones should be performed in ALL individuals with a new diagnosis of diabetes.<\/strong><\/p>\n\n\n\n

Type 2 Diabetes <\/em><\/em><\/p>\n\n\n\n

This results from a relative deficiency of and\/or insensitivity to insulin and is more commonly diagnosed in older people, although can occur in young (especially obese) individuals. It is more common in people of South-Asian and Afro-Caribbean heritage.<\/p>\n\n\n\n

Although the onset of type 2 diabetes is less dramatic than that of type 1 diabetes, the long-term sequelae are similar and equally devastating, as both Type 1 and Type 2 patients are at risk of developing the microvascular and macrovascular complications of the disease. <\/p>\n\n\n\n

Monogenic Diabetes<\/em><\/p>\n\n\n\n

These are rare forms of diabetes due to mutations in single genes; they are inherited in an autosomal dominant fashion. There are multiple different forms and the management principles depend on the specific gene involved. A diagnosis of monogenic diabetes should be suspect in individuals who do not demonstrate typical features of type 1 or type 2 diabetes. Further information about these forms of diabetes can be found at www.diabetesgenes.org<\/strong><\/a><\/p>\n\n\n\n

Pancreatic Diabetes (Type 3c diabetes)<\/em><\/p>\n\n\n\n

Diabetes may be caused by disorders of the pancreas such as chronic pancreatitis, haemochromatosis, cystic fibrosis, pancreatic cancer and post-pancreatic surgery. The diagnosis of these forms of diabetes may be obvious depending on previous history, but these forms of diabetes should be considered in all individuals whose presenting features are not typical of type 1 or type 2 diabetes.<\/p>\n\n\n\n

Steroid-Induced Diabetes<\/em><\/p>\n\n\n\n

High doses of steroids, such as prednisolone or dexamethasone, can induce diabetes in susceptible individuals, i.e. older age and overweight. Individuals with an HbA1c in the pre-diabetic range (42-47 mmol\/mol) are highly likely to develop diabetes if commenced on steroids. Consider checking an HbA1c in individuals at risk. If in the diabetes or pre-diabetes range then early commencement of blood glucose monitoring is recommended (see Steroid Safety guidance on RefHelp).<\/p>\n\n\n\n

Pre-Diabetic States<\/em><\/p>\n\n\n\n

Impaired Glucose Tolerance (IGT)<\/u><\/p>\n\n\n\n

IGT is a state of impaired glucose regulation, diagnosed on glucose tolerance testing, which confers an increased risk of future diabetes of 2-5% per year.  Patients with IGT tend to have higher blood pressure and plasma triglycerides when compared to non-diabetic individuals.<\/p>\n\n\n\n

Impaired Fasting Glycaemia (IFG)<\/u><\/p>\n\n\n\n

The term IFG classifies individuals with fasting plasma glucose (FPG) values above the normal range but below those diagnostic of diabetes i.e. FPG 6.1 mmol\/L – 6.9mmol\/L.   All such individuals should have a HbA1c checked to exclude a diagnosis of diabetes (see diagnosis of diabetes in asymptomatic individuals)<\/p>\n\n\n\n

Pre-diabetes<\/p>\n\n\n\n

HbA1c between 42-47 is considered a pre-diabetic state.<\/p>\n\n\n

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\"Diabetes
NHS Lothian<\/span><\/figcaption><\/figure>\n<\/div>\n\n\n

Gestational Diabetes Mellitus (GDM)<\/h4>\n\n\n\n

GDM is defined as carbohydrate intolerance of variable severity with onset or first recognition during pregnancy. GDM is still diagnosed using an oral glucose tolerance test (OGTT) and this is essentially the only situation now when an OGTT should be performed in primary care. The diagnostic criteria are different to that for standard diabetes: fasting glucose \u2265 5.3 mmol\/l and\/or 2hr glucose \u22659.0 mmol\/l<\/strong>. Women with risk factors for GDM, e.g. family history of type 2 diabetes, high risk ethnic group, previous large baby, elevated BMI, will have an OGTT arranged by their community midwife at 24-28 weeks.<\/p>\n\n\n

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\"Diabetes
NHS Lothian<\/span><\/figcaption><\/figure>\n<\/div>\n\n\n

Making a Diagnosis of Diabetes<\/strong><\/p>\n\n\n\n

Consider a diagnosis of diabetes in a person with potential symptoms<\/strong> of diabetes:<\/p>\n\n\n\n