Reasoning GP · Algorithm · 1-page summary
Raised creatinine or falling eGFR
For: adults in primary care with a raised creatinine, a low or falling eGFR or an AKI alert. Not for: children or pregnancy (specialist pathways); established CKD management (see the CKD protocol).
Core rule: compare with the patient's own baseline creatinine — a change is AKI until proven otherwise; check potassium, stop NSAIDs and hold the sick-day drugs with a written restart plan.
0Stop — call 999 now
- Potassium ≥6.5 mmol/L, or hyperkalaemic ECG changes, or palpitations, weakness, syncope → 999
- Sepsis high-risk features (new confusion, systolic ≤90, HR >130, RR ≥25, SpO₂ <92%), pulmonary oedema, uraemia (drowsy, asterixis, pericardial rub) → 999
- Anuria with deterioration, or fever + loin pain + suspected obstruction (pyonephrosis) → 999. Do not give fluid to an overloaded patient.
1Triage — AKI or CKD? (NICE NG148 / NG203)
| Finding | Meaning → action |
|---|---|
| Rise ≥26 µmol/L in 48 h | AKI → stage and find cause |
| Rise ≥50% in 7 days | AKI (urine <0.5 mL/kg/h >6 h also) |
| Stage 2–3 | ≥2× baseline, or ≥354 µmol/L acute → Same-day hospital |
| New low eGFR, well | Repeat U&E within 2 weeks |
| eGFR <60 >3 months | CKD → stage G and A (ACR) |
Stage on creatinine, not eGFR. No baseline → treat as possible AKI and repeat.
2Screen — serious causes
- Potassium 6.0–6.4 with AKI → ECG, Same-day hospital. 5.5–5.9 → exclude pseudohyperkalaemia, repeat.
- Blood + protein on dipstick with AKI (vasculitis, GN) → Same-day nephrology discussion.
- Retention / palpable bladder → catheterise, Same-day assessment.
- Myeloma: 60+ with bone pain or unexplained fracture → FBC, calcium, ESR/PV, electrophoresis, free light chains (within 48 hours if hypercalcaemia or leukopenia); suggestive → Suspected cancer. Hypercalcaemia or cord compression → Same-day
- Oliguria <0.5 mL/kg/h for 6 hours or more → Same-day hospital.
3Assess
☐ Obs, lying/standing BP, volume status ☐ Bladder, PR if needed ☐ Dipstick before catheter, ACR ☐ U&E, bicarbonate, FBC, CRP, bone profile, glucose ☐ Every drug incl. OTC NSAIDs ☐ ECG if K⁺ ≥6.0
Ultrasound within 24 hours if obstruction possible or no clear cause (6 hours if pyonephrosis). KFRE only in confirmed CKD G3–G5, never during AKI.
4Classify — only if blocks 0–2 are negative
- Pre-renal (commonest) — dehydration, sepsis, heart failure, ACEi/ARB + diuretic → fluids, drug review.
- Drug-induced — NSAIDs, "triple whammy", lithium, interstitial nephritis → stop the drug.
- Post-renal — prostate, retention, constipation, stones → catheter, ultrasound.
- Intrinsic — vasculitis, myeloma, rhabdomyolysis → specialist the same day.
- CKD — stable slow decline over months → confirm at 3 months, start CKD bundle.
- Uncertain — repeat U&E promptly, dipstick, ultrasound, renal advice and guidance.
5Treat today — doses: NICE/SPC, BNF, local formulary
- Stop NSAIDs; hold ACEi/ARB, diuretics, SGLT2 inhibitor, metformin individually (care in heart failure); write the restart plan.
- Stage 1 at home only if well, clear cause, drinking, no oliguria: oral fluids, treat cause, U&E within 24–48 hours.
- Dose-adjust renally cleared drugs (lithium, DOACs, gabapentinoids, opioids, nitrofurantoin).
- Confirmed CKD: ACEi/ARB if ACR criteria met, SGLT2i if eligible, atorvastatin 20 mg.
6Refer routinely and review
- Nephrology (NG203): KFRE >5%, ACR ≥70, ACR ≥30 + haematuria, eGFR fall ≥25% with category change or ≥15 in 12 months, BP uncontrolled on 4 or more drugs.
- After AKI: review at 3 months — U&E, ACR, BP (NICE QS76).
7Never reassure by
- A "normal" eGFR in a rapidly changing creatinine — eGFR lags.
- Low creatinine in a frail, low-muscle patient.
- A single eGFR — CKD needs 3 months.
- Restarting ACEi/ARB without a repeat U&E.
- A negative dipstick for protein — it misses myeloma light chains.
- Stopping a heart-failure diuretic without a plan.
8Safety-net — say it, then document it
999 “If you collapse, have chest pain or severe breathlessness, or your heart is racing, call 999.” Same-day “If you are passing much less urine, can't keep fluids down, or feel very drowsy or confused, contact us the same day or call 111.”
Recheck U&E on the agreed date; named clinician acts on the result. Telephone or remote consultation with any 999 feature → convert to 999, not a later appointment.
✓Safe to leave primary care only if — all five, documented
No block 0–2 feature; K⁺ known
Baseline found; AKI stage recorded
Well, drinking, clear reversible cause
Drugs held with restart plan
Repeat U&E booked; safety-net given
Summary of the full Reasoning GP raised creatinine algorithm, which holds the history, differential, investigations, lifestyle and evidence. Sources: NICE NG148 (AKI), KDIGO 2012, NICE QS76, NG203 (CKD), UK Kidney Association hyperkalaemia 2023, NG12 (suspected cancer, updated April 2026), NG253 (sepsis). Clinical reference — follow local renal pathways and check doses: NICE/SPC, BNF.