Kidney Health 9 min read·Updated 22 July 2026 Clinician-reviewed

Acute Kidney Injury (AKI)

A UK Consultant Nephrologist on acute kidney injury — the sudden, often reversible form of kidney failure that can develop in hours and needs urgent recognition.

  • Clinically Reviewed
  • NHS & NICE Aligned
  • UK Evidence-Based
  • Last Reviewed 22 July 2026

Professor Mohammed Mahdi Althaf

Consultant Nephrologist & Acute Physician

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Professor Mohammed Mahdi Althaf

MD, MSc, PgDip (Clin Ed), FRCP, FHEA, FASN

Consultant Nephrologist & Acute Physician · GMC 7216325

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Direct answer

Acute kidney injury (AKI) is a sudden drop in kidney function. Warning signs include reduced urine, swelling, confusion and nausea. Common triggers are dehydration, sepsis, blocked urine flow and nephrotoxic drugs. Most people recover with prompt treatment, but AKI can be life-threatening if missed.

Key recommendation: AKI develops over hours to days — it is sudden, unlike slow CKD.

Quick answer

✓ Best choices

  • Adequate fluids once your team confirms it is safe (often 1.5–2 L/day)
  • Easily digested, nutrient-dense meals during recovery
  • Vegetables, fruit, oats and whole grains as appetite returns
  • Protein in modest portions — typically 0.8–1.0 g/kg/day unless advised otherwise

✓ Foods to limit

  • NSAIDs (ibuprofen, naproxen, diclofenac) — they are nephrotoxic
  • Very salty, processed or ultra-processed foods
  • Alcohol while bloods are still recovering

Key takeaway

Acute kidney injury (AKI) is a sudden drop in kidney function. Warning signs include reduced urine, swelling, confusion and nausea. Common triggers are dehydration, sepsis, blocked urine flow and nephrotoxic drugs. Most people recover with prompt treatment, but AKI can be life-threatening if missed.

Who should be cautious

People on dialysis, post-transplant, pregnant or breastfeeding, or taking prescription medication — confirm with your renal team before changes.

Acute Kidney Injury (AKI)

AKI vs CKD

Chronic kidney disease (CKD) develops slowly over months to years. Acute kidney injury (AKI) develops over hours to days. CKD is usually irreversible; AKI is often reversible. However, an episode of AKI can leave lasting kidney damage (AKI-CKD transition), and people with existing CKD are at higher risk of AKI. The NHS 'sick-day rules' are designed to protect people with CKD from AKI during illnesses causing dehydration.

The three types of AKI

Pre-renal (most common): reduced blood flow to the kidneys — dehydration, sepsis, heart failure, bleeding, or NSAID/ACE inhibitor use during illness. Intrinsic: direct damage to kidney tissue — acute glomerulonephritis, contrast dye nephropathy, rhabdomyolysis (muscle breakdown), or interstitial nephritis from drugs. Post-renal: blockage of urine flow — enlarged prostate, kidney stones, tumours, or catheter blockage.

Kidney Vitality is a daily multivitamin developed by a UK Consultant Nephrologist using renal nutrition principles. It contains no added potassium, magnesium, phosphorus or iron, and no herbal blends. See the formulation.

Sick-day rules — protecting your kidneys during illness

If you have CKD and develop vomiting, diarrhoea, fever, or are not drinking normally, NICE advises temporary stopping of: ACE inhibitors (e.g., ramipril, lisinopril), ARBs (e.g., losartan, valsartan), NSAIDs (e.g., ibuprofen, naproxen), and diuretics (water tablets) in some cases. Restart them when you are eating and drinking normally again — usually within 24–48 hours. Contact your GP or renal team for personalised advice.

Diagnosis and treatment

AKI is diagnosed by a rise in serum creatinine and often a drop in urine output. An ultrasound checks for blockage. Treatment depends on cause: IV fluids for dehydration, antibiotics for sepsis, relieving blockage (catheter or stent), and stopping nephrotoxic drugs. In severe cases, temporary dialysis is needed until the kidneys recover.

Recovery and follow-up

Recovery time varies from a few days to several weeks. After AKI, NICE recommends checking eGFR at 3 and 6 months to ensure recovery and detect any lasting CKD. Some people need long-term nephrology follow-up. Preventing future AKI means staying hydrated during illness, avoiding NSAIDs, following sick-day rules, and telling any doctor you see that you have had AKI.

Kidney Disease Symptoms — Stage by Stage
Related reading: Kidney Disease Symptoms — Stage by Stage.

Key practical tips

Designed for quick scanning — what to order, what to avoid, sensible portions, common mistakes.

  • Follow the NHS sick-day rules: stop ACE inhibitors, ARBs, NSAIDs and diuretics when dehydrated
  • Re-check eGFR at 3 and 6 months as NICE recommends
  • Tell every clinician you see that you have had AKI

Clinical guidance

TL;DR summary

Acute kidney injury (AKI) is a sudden drop in kidney function. Warning signs include reduced urine, swelling, confusion and nausea. Common triggers are dehydration, sepsis, blocked urine flow and nephrotoxic drugs. Most people recover with prompt treatment, but AKI can be life-threatening if missed.

Key takeaways
  • AKI develops over hours to days — it is sudden, unlike slow CKD.
  • Warning signs: reduced urine, swelling, confusion, dark urine.
  • Common triggers: dehydration, sepsis, NSAIDs, blocked urine flow.
  • Most AKI is reversible with fluids and treating the cause.
  • Sick-day rules: stop ACE inhibitors, ARBs and NSAIDs when dehydrated.
Kidney Diet & Nutrition Considerations

After acute kidney injury (AKI) the priority is recovery: rehydration, treating the underlying cause, stopping nephrotoxins and giving the kidneys a calm nutritional environment. Once eGFR is recovering, a balanced Mediterranean-style diet with sensible salt, sensible protein and good hydration supports healing — and reduces the risk of AKI tipping into long-term CKD.

Foods to prioritise

  • Adequate fluids once your team confirms it is safe (often 1.5–2 L/day)
  • Easily digested, nutrient-dense meals during recovery
  • Vegetables, fruit, oats and whole grains as appetite returns
  • Protein in modest portions — typically 0.8–1.0 g/kg/day unless advised otherwise

Foods to limit

  • NSAIDs (ibuprofen, naproxen, diclofenac) — they are nephrotoxic
  • Very salty, processed or ultra-processed foods
  • Alcohol while bloods are still recovering

Potassium, phosphate and protein needs vary between individuals — please confirm personal targets with your renal team or dietitian. Browse the Kidney Diet Hub for more guides in this cluster.

Frequently asked questions

What is acute kidney injury (AKI)?

Acute kidney injury is a sudden drop in kidney function over hours to days. It is not the same as chronic kidney disease (CKD), which develops slowly over years. AKI is usually reversible if the cause is treated quickly — but it can be life-threatening if missed.

What are the warning signs of AKI?

Reduced or no urine output, sudden ankle or facial swelling, confusion or drowsiness, severe fatigue, shortness of breath, nausea, and dark or tea-coloured urine. In people who are already unwell with diarrhoea, vomiting, sepsis, or dehydration, AKI can develop rapidly.

What causes AKI?

Common causes include dehydration from vomiting/diarrhoea (especially with NSAID use), sepsis, major surgery, blocked urine flow (enlarged prostate, kidney stones), nephrotoxic drugs (NSAIDs, some antibiotics, contrast dye for scans), and severe infections.

Can you recover from acute kidney injury?

Yes — many people recover fully, especially with prompt fluid replacement and treatment of the underlying cause. Recovery can take days to weeks. Some people are left with reduced kidney function (AKI-CKD transition) and need long-term monitoring.

What should I eat to recover from acute kidney injury?

Most adults recovering from AKI do best on a balanced Mediterranean-style diet with adequate hydration (once your team confirms it's safe), moderate protein (around 0.8–1.0 g/kg/day), lower salt, and avoidance of NSAIDs. Your renal team will give you personalised fluid and protein targets based on your recovery.

Nutritional challenges in kidney disease

Many people living with kidney disease have to limit foods because of potassium, phosphate, diabetes, dialysis, appetite changes or simply the time it takes to cook from scratch every day. That can make it harder to keep daily nutrition balanced — particularly for vitamins and minerals that food alone may not fully cover.

Kidney Vitality is a UK-formulated daily nutritional support product designed by Consultant Nephrologist Professor Mohammed Mahdi Althaf with renal nutrition in mind from the start. It keeps doses moderate, leaves out added potassium, phosphate and magnesium, and avoids megadose vitamin A — sitting alongside a kidney-friendly diet, not replacing it.

Why Kidney Vitality fits this need

Built around UK renal guidance

Aligned with NICE NG148 (AKI), NICE NG203 (CKD), and UK Kidney Association AKI guidance.

Designed by a UK Consultant Nephrologist

Formulated and reviewed by Professor Mohammed Mahdi Althaf (GMC 7216325).

Evidence-based by design

Urgent safety-netting advice and NHS sick-day rule guidance.

Designed by a UK Consultant Nephrologist

Ready to support your kidney health?

If you have been researching kidney health, supplements, CKD nutrition or kidney-friendly living, Kidney Vitality was developed specifically around those principles by Professor Mohammed Mahdi Althaf (GMC 7216325). Nephrologist Developed Daily Multivitamin.

  • No Added Potassium
  • No Added Magnesium
  • No Added Phosphorus
  • No Added Iron
  • One capsule daily
  • UK GMP — BRCGS, NSF GMP, Halal
Subscribe & Save — £20.39/monthCheck your current multivitamin

✓ Free UK tracked delivery  ·  ✓ Delivered every 30 days  ·  ✓ Pause or cancel anytime  ·  ✓ Never run out

ComparisonKidney VitalityTypical high-street multivitamin
Added potassiumNoneOften included
Added phosphateNoneOften included (E338–E452)
Vitamin A (retinol)No megadoseOften high-dose retinol
Kidney-focused formulationYesNo — general population
Consultant Nephrologist involvementYes (GMC 7216325)No
UK GMP manufacturedYes (BRCGS, NSF GMP)Varies

Food supplement. Not a medicine and not a treatment for kidney disease. Speak with your GP, pharmacist or renal team before starting any new supplement, especially in advanced CKD, on dialysis, post-transplant, pregnant or breastfeeding.

Clinical reviewer

Professor Mohammed Mahdi Althaf

Consultant Nephrologist

Acute Physician

GMC 7216325

View Full Biography

Professor Mohammed Mahdi Althaf is a UK Consultant Nephrologist and Acute Physician with a special interest in chronic kidney disease, AKI prevention and renal nutrition. He combines hospital practice with patient education and clinical guidance review.

View professional profile →
View Credentials
  • MD
  • MSc
  • PgDip (Clin Ed)
  • FRCP
  • FHEA
  • FASN

About this article

Written for UK patients and based on:

  • NICE guidance
  • NHS resources
  • British Dietetic Association guidance
  • Kidney Care UK resources
View methodology

Each article is researched against current UK clinical guidance (NICE NG203, NG118, NG136), NHS patient resources, KDIGO and KDOQI international guidelines, and the British Dietetic Association Renal Nutrition Group. Drafts are written by the Kidney Vitality editorial team and reviewed by a UK Consultant Nephrologist before publication. Content is reviewed on a rolling basis and updated when guidance changes.

Editorial standards

  • Clinically reviewed
  • NHS-aligned
  • NICE-aligned
  • Evidence-based
  • Reviewed before publication
View full editorial process

Every article is researched and written by the Kidney Vitality editorial team using current UK clinical guidance (NICE NG203, NG118, NG136), NHS patient resources, KDIGO/KDOQI international guidelines, and British Dietetic Association renal nutrition guidance. Drafts are reviewed for clinical accuracy by Professor Mohammed Mahdi Althaf, MD, MSc, PgDip (Clin Ed), FRCP, FHEA, FASN (Consultant Nephrologist & Acute Physician, GMC 7216325) before publication. Content is updated when UK guidance changes.

References (4)View Sources
  1. NICE NG203: Chronic kidney disease — assessment and management
  2. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD
  3. KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update
  4. British Dietetic Association — Renal Nutrition Group

Medical disclaimer

This content is educational only and does not replace personalised medical advice.

Read full disclaimer

This page is general information, not personal medical advice. If you have chronic kidney disease, are on dialysis, have had a kidney transplant, are pregnant or breastfeeding, or take prescription medication, please confirm any supplement with your GP, pharmacist or renal team before starting.

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