Laboratory Results, Organ Function and Drug Concentrations
Interpret relevant laboratory results or medicine concentrations and determine their implication for ongoing treatment.
How to prepare for the PSA
Combine patient-centred prescribing judgement with fast BNF navigation, reliable calculations, complete prescriptions and explicit monitoring and communication.
Core concepts
Concept 1
Data Interpretation items focus on what investigation results mean for prescribing, not on making a diagnosis for its own sake.
Exam cue: Identify which result is linked to efficacy, toxicity or medicine clearance.
Concept 2
Kidney function, liver tests, blood counts, electrolytes and medicine concentrations must be read in context, with units, timing and trends.
Exam cue: Check units, sampling time, baseline and trend before acting on a concentration.
Concept 3
The prescribing response may be to withhold, reduce, continue unchanged, increase or replace treatment.
Exam cue: Translate the data into the smallest safe prescribing change supported by the scenario.
Risk pitfalls and guardrails
Treating a laboratory flag as an automatic instruction to stop every related medicine.
Guardrail: Do not let a familiar medicine, reference search or calculator output replace patient-specific safety checks and escalation.
Ignoring when a drug concentration was sampled.
Guardrail: Do not let a familiar medicine, reference search or calculator output replace patient-specific safety checks and escalation.
Making a diagnostic conclusion without answering the prescribing decision.
Guardrail: Do not let a familiar medicine, reference search or calculator output replace patient-specific safety checks and escalation.
Memory anchors
Prescribing Focus
Use the data to decide what should happen to treatment.
Units
Read the result, reference information and medicine instruction in compatible units.
Sampling Time
Interpret a medicine concentration only with its timing relative to dosing.
Organ Function
Changing kidney or liver function can alter medicine exposure and safety.
Five Actions
Consider withhold, reduce, no change, increase or start an alternative.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
A patient on ramipril has potassium 6.2 mmol/L. What is the prescribing implication?
A patient on metformin has eGFR 18 mL/min/1.73 m². What is best?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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