Recurrent Hypoglycaemia in a Patient With Type 2 Diabetes and Declining Renal Function
A 72-year-old woman with a 14-year history of type 2 diabetes attends for review. Her medications are metformin 1 g twice daily, gliclazide modified-release 60 mg each morning, ramipril 5 mg, atorvastatin 20 mg and aspirin 75 mg. Over the past 3 months she has had four episodes of symptomatic hypoglycaemia, two of them at night, one requiring her daughter to call an ambulance. Her HbA1c is 6.1% (43 mmol/mol). Recent bloods: creatinine 168 micromol/L with an estimated glomerular filtration rate of 28 mL/min/1.73 m2, haemoglobin 104 g/L, albumin 33 g/L. She lives alone, eats one small cooked meal daily, and reports no awareness of sweating or tremor before the episodes. She asks whether she should stop checking her glucose because 'the numbers are good'.
1. Account for the hypoglycaemia by identifying the pharmacological and physiological contributors in this patient.
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The hypoglycaemia is iatrogenic and multifactorial, and the 'good' HbA1c is a warning sign rather than reassurance.
Drug factors: Gliclazide is a sulfonylurea and acts by closing pancreatic beta-cell potassium channels to stimulate insulin release irrespective of the prevailing glucose; it can therefore cause prolonged and recurrent hypoglycaemia, particularly in older adults. Its metabolites are renally cleared, so accumulation occurs as kidney function falls. Metformin itself does not cause hypoglycaemia but is relatively contraindicated at an eGFR of 28 and contributes to gastrointestinal intolerance and reduced intake, which lowers glucose indirectly.
Renal factors: At an eGFR of 28 mL/min/1.73 m2, insulin is cleared more slowly and renal gluconeogenesis is impaired, so both exogenous and endogenous insulin have a longer and more powerful effect. This is the single most important reason the sulfonylurea dose is now unsafe.
Nutritional and social factors: One small meal a day, living alone, and low albumin (33 g/L) indicate poor intake and frailty, reducing substrate availability and glycogen reserve. Alcohol, if present, would compound this.
Impaired awareness: She reports no warning symptoms, which is a recognised complication of recurrent hypoglycaemia and of long-standing diabetes; this removes her main defence and raises the risk of severe events.
Age and targets: An HbA1c of 6.1% in a frail 72-year-old on a sulfonylurea is over-treatment; guideline-consistent targets for someone with frailty and comorbidity are considerably higher, and the priority is avoiding hypoglycaemia rather than achieving a low average.
2. Set out your medication changes and monitoring plan, and explain what you would tell her about glucose self-monitoring.
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Medication changes:
- Stop gliclazide. It is the proximate cause of recurrent hypoglycaemia and is unsafe with an eGFR of 28. Tapering is not required for hypoglycaemia risk, but she should be warned that glucose may rise and that this is acceptable.
- Stop metformin. At an eGFR below 30 it should not be continued because of lactic acidosis risk; document the reason in the record.
- Review ramipril - acceptable to continue for renal protection but check potassium and creatinine after any change, and hold during acute illness.
- Consider a safer glucose-lowering agent if control drifts - for example a DPP-4 inhibitor with renal dose adjustment, chosen with attention to cost and local formulary; insulin, if eventually needed, should be started at low dose with structured education and support, not as a quick fix.
- Deprescribe aspirin if there is no established cardiovascular disease, given bleeding risk in a frail older adult; review statin dose for tolerability.
Targets: Relax the HbA1c target to roughly 7.5-8.5% (or an equivalent individualised range) and state explicitly that the goal is freedom from hypoglycaemia.
Monitoring: Capillary glucose at least twice daily and before driving, with a written log; a review in 2 weeks and repeat renal function, electrolytes and full blood count. Screen for frailty, falls and vision. Consider a continuous glucose sensor if available, particularly to detect nocturnal events.
What to tell her about self-monitoring: Do not stop checking - the numbers were 'good' because the medication was too strong, not because she was well. Monitoring is now the tool that proves the new regimen is safe, especially overnight and when she eats poorly. She should treat any reading below 4 mmol/L with 15-20 g of fast-acting carbohydrate, recheck in 15 minutes, and follow with a snack. She needs a glucagon kit or written emergency plan and a named contact, and she should be advised not to drive during a low and to check before driving.