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Low urine output

Asked to see

Oliguria = urine output <0.5 mL/kg/h for more than 6 hours (an AKI criterion). Check the catheter before anything else.

Act now

  1. 1

    Flush or replace a blocked catheter; catheterise for retention.

  2. 2

    Fluid challenge if hypovolaemic and no overload (see IV fluids).

Assess

  • Is the catheter blocked or kinked? Bladder scan if no catheter.
  • Fluid status, BP, sepsis signs, drug chart, recent contrast.

Investigations

  • U&E compared with baseline creatinine, venous gas (K⁺, pH), urine dipstick, FBC, CRP.
  • Urinary tract ultrasound within 24 hours if no cause found or obstruction suspected; within 6 hours if pyonephrosis suspected.

Manage

  • Stop or hold nephrotoxic and AKI-risk drugs: NSAIDs, ACE inhibitors/ARBs, diuretics, aminoglycosides, and review metformin and others.
  • Treat sepsis; strict fluid balance; daily weights.
  • Hyperkalaemia: see that topic.

Escalate when

  • Refractory hyperkalaemia, acidosis, fluid overload or uraemic complications: urgent renal/critical care (renal replacement therapy).
  • AKI stage 3, suspected intrinsic renal disease, or renal transplant: discuss with nephrology.

Written to current guidance (NICE NG148, CG174) · sources checked 14 Nov 2026. We watch NICE for updates weekly.

Sources (2)

Reviewed by Aboodee Alhasso, MPharm MRCPharm IP on 14 Nov 2026

Calculators for this

For healthcare professionals, as an aid to clinical judgement — not a substitute for it. Follow your local policy and ask a senior when in doubt.