Type 1 diabetes

• Type 1 diabetes is characterised by an inability of the pancreas to produce/secrete insulin due to autoimmune destruction of the beta cells in the pancreatic islets of langerhan
• Type 1 diabetes may present with the classic triad of symptoms of hyperglycaemia:

  • Polyuria (excessive urine)
  • Polydipsia (excessive thirst)
  • Weight loss (mainly through dehydration)

  Alternatively, patents may present with diabetic ketoacidosis
• Make an initial diagnosis of T1DM on clinical grounds in patients presenting with hyperglycaemia. Usually have 1 or more of:

  • Ketosis
  • Rapid weight loss
  • Age of onset under 50 years
  • BMI below 25
  • Personal and/or family history of autoimmune disease
• Serum C peptide and autoantibodies can be measured if there is doubt over the type 1 diabetes diagnosis
• Management of T1DM:

  • Subcutaneous insulin - first line is basal-bolus regime
  • Monitoring dietary carbohydrate intake
  • Monitoring blood sugar levels upon waking, at each meal and before bed
  • Monitoring for and managing complications
  • Intensive management of those with cardiovascular risk factors - ARB is the first line treatment for hypertension with T1DM
• Basal-bolus regime:

  • Twice daily insulin detemir as basal insulin therapy
  • Rapid acting insulin analogues that are injected before meals - novorapid or humalog
  • Ensure patients rotate injection site as lipodystrophy can occur - insulin will not be properly absorbed
• Rapid-acting insulins (e.g., NovoRapid) start working after around 10 minutes and last about 4 hours.
• Short-acting insulins (e.g., Actrapid) start working in around 30 minutes and last about 8 hours.
• Intermediate-acting insulins (e.g., Humulin I) start working in around 1 hour and last about 16 hours.
• Long-acting insulins (e.g., Levemir and Lantus) start working in around 1 hour and last about 24 hours or longer.
• Combinations insulins contain a rapid-acting and intermediate-acting insulin. In brackets is the ratio of rapid-acting to intermediate-acting insulin:

  • Humalog 25 (25:75)
  • Humalog 50 (50:50)
  • Novomix 30 (30:70)

   
• Support adults with type 1 diabetes to aim for a target HbA1c level of 48 mmol/mol (6.5%) or lower, to minimise the risk of long‑term vascular complications. It should be measured every 3-6 months.
• Measure diabetes-specific autoantibodies in adults with an inital diagnosis of T1DM:

  • Islet cell antibodies (ICA)
  • Glutamic acid decarboxylase antibodies
  • Insulin antibodies
  • IA-2 antibodies
• If type 1 diabetes is diagnosed in an adult, immediate (same-day) referral to a multidisciplinary diabetes specialist team should be arranged.
• Diagnosis if patient symptomatic:

  • A random venous plasma glucose concentration 11.1 or higher
  • A fasting plasma glucose 7.0 or higher
• If no symptoms are present, diagnosis should not be based on a single glucose determination but requires confirmatory plasma venous determination on two or more occasions
• Patients ≥60 years old presenting with weight loss and new-onset diabetes should be investigated for pancreatic cancer (e.g. CT/MRI imaging of the pancreas).
• Target blood glucose levels:

  • 5-7 upon waking
  • 4-7 before meals
  • 5-9 post meal
• C-peptide measures how much insulin is being produced by the pancreas - low in T1DM
• Anti-GAD is the most commonly identified autoantibody in T1DM