A 14 year old boy presents with nausea, vomiting and malaise for 2 days. There was no history of fever or system specific symptoms.

His medical history is significant for mild intermittent asthma since age 8. He visited his primary care practitioner 5 days ago with an exacerbation, which was treated with oral prednisolone for 3 days.

A FBC is within normal limits, but a serum electrolyte assay reveals a potassium level of 6.0 mEq/L; this is repeated and re-confirmed.

An ECG is found to be completely normal. His random capillary glucose is 120 mg/dl.