Overview
Diabetes is an endocrine disease that results from a lack of or reduced effectiveness fo insulin. The main metabolic derangement is hyperglycaemia, which can lead to serious microvascular and macrovascular complications.
Both T1DM and T2DM have the same long-term complications. Diabetes (especially T2DM) will most frequently be diagnosed on screening. Some T1DM patients may present in Diabetic Ketoacidosis (DKA), while some T2DM patients may present in Hyperosmolar Hyperglycemic State (HHS).
Definition of terms
| Type | Description |
|---|---|
| Type I Diabetes Mellitus (T1DM) | Caused by autoimmune destruction of beta cells. Always requires insulin. Lean patient with early onset. |
| Type II Diabetes Mellitus (T2DM) | Caused by insulin resistance. Controlled by appropriate diet and exercise and/or oral meds. May require insulin. Chronically overweight/obese patient. |
| Maturity Onset Diabetes of the Young (MODY) | An autosomal dominant form of T2DM that affects young individuals |
| Impaired Glucose Regulation (IGR) | Includes Impaired Glucose Tolerance (IGT) and Impaired Fasting Glucose (IFG) |
| Impaired fasting glucose (IFG) | Fasting glucose 6.1 – 7 mmol/L due to hepatic insulin resistance |
| Impaired glucose tolerance (IGT) | 2-hour OGTT 7.8 – 11.1 mmol/L due to muscle insulin resistance. More likely to develop T2DM and cardiovascular disease than IFG. |
- Key symptoms
- Polyuria (because the patient has glucose in urine)
- Polydipsia (because the patient is dehydrated)
- Polyphagia (because the patient is hungry)
Screening for Diabetes Mellitus
Screening for DM can be done with an HbA1C level, fasting plasma glucose, or Oral Glucose Tolerance Test (OGTT). If fasting plasma glucose is used alone for screening, ≥ 2 abnormal readings are needed to make the diagnosis. The next best step after diagnosing diabetes is to get a HbA1C level, as this will give an idea of glycemic control over the past 3 months and will be used to dictate therapy.
| Diagnosis | HbA1C | Fasting glucose (mmol/L) | Glucose Tolerance (mmol/L) |
|---|---|---|---|
| No diabetes | < 5.7% | ≤ 5.6 | ≤ 7.8 |
| Pre-diabetes (IGR) | 5.7 – 6.5 | 5.6 – 6.9 (IFG) | 7.8 – 11.0 (IGT) |
| Diabetes | ≥ 6.5% | ≥ 7.0 | ≥ 11.1 |
- Situations where HbA1C cannot be used for diagnosis
- Hemoglobinopathies
- Haemolytic anaemia
- Untreated iron deficiency anaemia
- Suspected gestational diabetes
- Children
- HIV
- Chronic kidney disease
- Medication that can cause hyperglycaemia e.g. corticosteroids
Management of Diabetes Mellitus
The main goal of managing diabetes is to minimise the probability of complications while maximising the patient’s quality of life.
When a new diagnosis of T2DM is made, a determination of how the patient is treated is based primarily on HbA1C levels AND whether or not they have complications. All newly diagnosed diabetics should be screened for complications at the first checkup after diagnosis. The best initial therapy in a new T2DM patient is metformin (unless contraindicated).
Target HbA1C is ≤ 6.5%, especially in young patients. May be lax in much older patients due to the risk of hypoglycemia. Follow up HbA1C every 3 – 6 months. Manage other comorbidities.
| HbA1C level (%) | Treatment |
|---|---|
| ≤ 7.5 | Monotherapy + lifestyle |
| 7.6 – 9 | Dual therapy |
| ≥ 9 without complications | Insulin (NPH +/- soluble insulin) |
| ≥ 9 with complications | Triple therapy |
- Dietary advice
- High fibre, log glycaemic index sources of carbohydrates
- Low-fat dairy products and oily fish
- Control intake of foods with saturated fats and trans fatty acids
