Synopsis
Use clinical observations, laboratory trends and treatment response to adjust prescribing, distinguishing a meaningful change in the patient from an isolated number or an inappropriate target.
- Identify the decision the data should inform, then check identity, units, timing, reliability and the relevant baseline before changing treatment.
- Combine the result with symptoms, examination, actual medicine use and the indication. A number within a population range can still be unsafe for the individual, and an abnormal value can sometimes be an expected monitored response.
- Distinguish stable impairment from acute deterioration. A chronic dose table cannot safely substitute for assessment of dehydration, sepsis, hypoxia or rapidly evolving organ injury.
Reasoning priorities
Establish whether the result supports a stable dose category or acute assessment.
Check patient identity, units, sample date and previous measurements. A laboratory eGFR during rapidly changing creatinine is not a dependable steady-state clearance. Assess intake, urine output and physiological stability before applying a chronic medicine dose limit to an acutely unwell person.
Worked reasoning
A 72-year-old takes metformin prolonged-release 2,000 mg orally with the evening meal and dapagliflozin 10 mg orally daily for type 2 diabetes. eGFR values over 3 months are 39, 38 and 38 mL/min/1.73 m². She is well hydrated without acute illness or hypoxia; HbA1c is 50 mmol/mol against an agreed 48–58 target. Her metformin tablets contain 500 mg.
- Identify the stable renal category rather than assuming an acute kidney injury from one result. The supplied repeated eGFR values place her in the selected metformin product’s 30–44 band, which permits a maximum total of 1,000 mg per day.
- Compare prescribed exposure with that ceiling: 2,000 mg daily is 1,000 mg above the permitted maximum. The revised 1,000 mg dose is two 500 mg prolonged-release tablets, representing a 50% reduction from the current daily amount.
- Give the final medicine action: reduce metformin prolonged release to 1,000 mg orally with the evening meal and update the supply instructions. Review dapagliflozin separately; reduced glucose efficacy at this eGFR does not automatically remove its eligible protective role in this stable patient.
- Arrange review of tolerability, glucose symptoms and renal trajectory, with repeat HbA1c around 3 months for this illustrative stable plan and earlier assessment if illness develops. Independently verify two 500 mg tablets equal 1,000 mg, confirm the old four-tablet instruction is inactive and explain the change and sick-day contact plan to the patient.