Type 1 Diabetes Mellitus

General Medicine

Autoimmune β-cell destruction with absolute insulin deficiency; lifelong insulin required.

History taking

  • Polyuria, polydipsia, weight loss
  • DKA episodes, hypoglycaemia awareness
  • Injection technique, glucose log

Examination

  • Weight, BMI, BP
  • Injection sites for lipohypertrophy
  • Fundi, feet, peripheral pulses

Red flags

  • DKA: vomiting, abdominal pain, Kussmaul breathing
  • Severe hypoglycaemia

Differential diagnosis

  • See differentials section per chief complaint

Recommended investigations

  • HbA1c 3-monthly
  • Annual lipids, eGFR, urine ACR
  • Annual retinal screening
  • TSH, coeliac screen

Diagnosis

  • Clinical diagnosis supported by targeted investigations

Initial treatment / management

  • Basal-bolus or pump therapy
  • Carbohydrate counting
  • CGM where available

Drug therapy

  • Basal: glargine/degludec 0.3–0.5 U/kg OD
  • Bolus: aspart/lispro with meals (ICR 1U:10g)
  • Glucagon kit for severe hypoglycaemia

Lifestyle advice

  • Consistent meal timing
  • Exercise with carb adjustment
  • Sick-day rules

Follow-up advice

  • 3-monthly HbA1c (target <7%)
  • Annual complication screen

Patient counselling

  • Sick-day rules
  • Hypoglycaemia recognition + 15-15 rule
  • Driving and DKA prevention

Referral criteria

  • Refer if diagnostic uncertainty, complications, or failure of first-line therapy

Clinical pearls

  • Never stop basal insulin even if not eating — risk of DKA

References

  • Harrison's Principles of Internal Medicine, 21e
  • NICE / WHO guidelines (current edition)

Educational outpatient guide — verify against local guidelines before clinical use.

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