The kidney filters and almost completely reabsorbs about 180 grams of glucose a day, contributes to gluconeogenesis, and adapts its handling of glucose in diabetes in ways that worsen hyperglycaemia rather than correct it. This review works forward from that physiology to the pharmacology of sodium-glucose cotransporter 2 inhibition, and then to why the class delivers renal and cardiovascular benefit disproportionate to its effect on HbA1c.
The useful part for a nephrologist is the framing. If the drug is understood as a glucose-lowering agent, its use in patients with modest hyperglycaemia or none at all looks like indication creep. Understood as an intervention on renal sodium and glucose handling — with downstream effects on tubuloglomerular feedback, intraglomerular pressure, tubular workload and oxygen consumption — the trial results across chronic kidney disease and heart failure stop looking anomalous.
That framing also explains the class's adverse effect profile. Glycosuria by design produces genital mycotic infection and volume-related effects; the shift in substrate handling produces euglycaemic ketoacidosis, which is the one that gets missed because the glucose is normal. Both are predictable from the mechanism rather than idiosyncratic.
- Describe the drug to patients as a kidney drug, not a diabetes drug, where the indication is kidney disease
- Expect and counsel for genital mycotic infection; it is a mechanism, not a complication
- Teach euglycaemic ketoacidosis explicitly — a normal glucose does not exclude it
- Give sick-day advice at the time of prescribing, not at the first illness
- Do not withhold the class because HbA1c is already acceptable
Why it matters
It reframes a drug class that many still position by its glucose effect, which is the smallest thing it does.
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