Capillary blood glucose testing

PLAB 2 & PRES 3 · practical skills / endocrine · easy · 8 minutes

Candidate brief

You are an FY2 doctor on a medical ward. Mr Samuel Okafor, 59, has type 2 diabetes treated with insulin and was admitted two days ago with a chest infection. The nurse tells you he has become shaky, sweaty and a bit muddled in the last few minutes and asks you to check his capillary blood glucose. Please perform the capillary blood glucose measurement, and manage what you find. Verbalise each step as you perform it.

What examiners look for

"Four is the floor." Below 4 mmol/L is hypoglycaemia and is treated on the number plus symptoms — and in a symptomatic patient, treatment begins with the first reliable low reading; it is never deferred for a confirmatory venous sample while the patient deteriorates. Wash the hands — the patient's, not just yours. Jam, fruit juice and glucose gel residue on skin are textbook causes of falsely high capillary readings. A reading that contradicts the patient's symptoms is a reading to repeat properly, not to file. Single-use lancets are non-negotiable. Finger-prick devices designed for one person must never be used on another — shared devices have caused hepatitis B outbreaks in care settings. In a practical exam, stating this unprompted is a recognised marker of safe practice. Treat, recheck, then sustain: fast-acting carbohydrate to correct, recheck in 10–15 minutes and repeat if still low, then longer-acting carbohydrate once recovered to prevent recurrence. Stopping at the first step is the commonest management gap. Hypoglycaemia on a ward is usually prescribed, not accidental: full insulin doses running against half-eaten meals during acute illness. The complete answer reviews the insulin chart with the team — treating the episode without reviewing the cause guarantees tomorrow's episode. Driving is part of discharge thinking for insulin-treated patients: episodes, awareness, DVLA notification and testing before driving all belong in the conversation once the patient has recovered — examiners reward the candidate who remembers the patient's life outside the ward.

Guideline references

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