Acute kidney injury assessment (Diagnostic assessment of acute kidney injury (AKI))
How a doctor finds out whether your kidneys have suddenly stopped working as well as they should, why it has happened, and what needs to be done about it.
✓ Medically reviewed by a GMC-registered consultant · last reviewed September 2026 · next review September 2027 · how we review
In short
- It confirms whether your kidneys have suddenly become less able to work, finds out why, and decides what treatment and monitoring you need.
- The most common causes are dehydration and reduced blood flow to the kidneys — often from vomiting, diarrhoea, infection or certain medicines.
- AKI often causes no obvious symptoms early on and is picked up on a blood test, so monitoring matters more than 'feeling fine'.
- Stopping certain medicines, treating infection and correcting dehydration can reverse many cases if acted on early.
A plain-English summary. The detail — including risks and recovery — is below.
At a glance
A general guide. Your specialist will give you advice for your situation.
Confirms AKI early, when many cases can still be reversed
A private outpatient assessment is the wrong setting for someone who is drowsy, barely passing urine, breathless or has signs of a dangerously high...
Blood and urine tests, medicine review and often an ultrasound. Treatment of the cause usually begins straight away.
A clear follow-up blood test to confirm whether kidney function has recovered.
Blood and urine tests, medicine review and often an ultrasound. Treatment of the cause usually begins straight...
Repeat blood tests show whether kidney function is stabilising or improving. Fluids, treatment of infection or...
Kidney function often recovers towards its previous level. Paused medicines are reviewed and carefully restarted...
A follow-up blood test confirms whether the kidneys have returned to baseline, and you are advised on protecting...
What is an acute kidney injury assessment?
Acute kidney injury (AKI) means the kidneys have suddenly become less able to do their job — clearing waste, balancing salts and managing the body's water. It is common, often reversible if caught early, but can be serious. The assessment is about confirming it, finding the cause, and deciding what to do.
AKI is usually picked up on a blood test showing a rising level of a waste product called creatinine, or by noticing that someone is passing much less urine. The assessment then looks for the cause: most often dehydration or reduced blood flow to the kidneys (for example from vomiting, diarrhoea, infection or certain medicines), sometimes a blockage in the urine system, and less often a problem within the kidney itself.
The doctor takes a history, examines you (including your fluid state and blood pressure), reviews your medicines, and arranges blood tests, urine tests and often an ultrasound of the kidneys. The aim is to treat the cause, protect the kidneys from further harm, and decide whether you need hospital care.
AKI itself often causes few symptoms early on, which is why it is frequently found on a blood test rather than because someone feels unwell from the kidneys directly.
Types, options & approaches
There may be different ways to do this. The right approach depends on the clinical question and your circumstances.
Options at a glance
These are the main approaches described in this guide. The right option depends on the diagnosis, your goals and what your clinician thinks is safe.
Blood tests (kidney function and more)
Creatinine and urea show how well the kidneys are clearing waste; a rise over hours to days defines AKI. Salts such as potassium are checked because a high potassium can be...
Urine tests
A simple dipstick and laboratory tests of the urine look for blood, protein and infection, which help point to the cause and to problems inside the kidney itself.
Kidney ultrasound
A scan with no radiation, mainly used to check for a blockage in the urine system (such as stones or an enlarged prostate) and to look at kidney size and structure. It is...
Medication and fluid review
A careful look at all medicines, because some (including certain blood-pressure tablets, anti-inflammatory painkillers and water tablets) can reduce kidney function or need...
Preparing for your test
- If you are very unwell — drowsy, barely passing urine, breathless, or with palpitations — seek urgent medical help rather than waiting for a routine appointment.
- Bring a full list of all your medicines, including over-the-counter painkillers and supplements, as some affect the kidneys.
- Note any recent vomiting, diarrhoea, fever, reduced drinking, or how much urine you have been passing.
- Mention any contrast scans, new medicines or recent procedures in the past days or weeks.
- Tell the team about diabetes, high blood pressure, heart failure or known kidney problems.
- You usually do not need to fast, but follow whatever the assessing unit advises on the day.
What happens
A doctor asks about your symptoms, recent illness, fluid intake and urine output, and reviews your medicines in detail. They examine you, paying attention to your fluid state, blood pressure and any sign of infection or a full bladder.
Blood tests are taken to confirm AKI and measure salts such as potassium. Urine is tested. An ultrasound of the kidneys is often arranged, especially to rule out a blockage. Based on the results, the team treats the cause — for example giving fluids for dehydration, treating an infection, relieving a blockage, or pausing medicines that are harming the kidneys.
Mild AKI may be managed with close monitoring and simple measures. More severe AKI, a dangerously high potassium, or signs of serious illness usually mean hospital admission, and occasionally temporary dialysis is needed.
Is this test right for me?
A good consultation should explore whether it's the right choice for you now — including reasons to wait or consider something else.
May not be suitable if…
- A private outpatient assessment is the wrong setting for someone who is drowsy, barely passing urine, breathless or has signs of a dangerously high potassium — these need urgent hospital care.
- It is not a screening test for the general well population; it responds to a rising creatinine, falling urine output or a clear risk.
- An assessment that only treats the kidney numbers, without finding and treating the cause, is inadequate.
- Where a problem within the kidney itself is suspected, a kidney specialist is needed rather than a general assessment alone.
Delay or rearrange if…
- There are signs of severe illness or a dangerously high potassium — do not delay, seek urgent hospital care.
- Recent medicine changes or contrast scans that are relevant have not yet been reviewed.
- Urine output or fluid state cannot be properly assessed in the available setting.
- Needed previous blood results, which define your usual baseline, are not available.
Alternatives to discuss
- Close monitoring with repeat blood tests and simple measures for mild AKI.
- Treating the underlying cause (rehydration, treating infection, relieving a blockage) as the main intervention.
- Referral to a kidney specialist when a kidney disease or severe AKI is suspected.
- NHS hospital admission when outpatient management is not safe.
Before you decide
Use this as a shared-decision checklist. The aim is not just “can this be done?”, but whether it is right for you, now, with the risks and alternatives clearly understood.
What matters most to me?
Think about symptoms, daily life, work, caring responsibilities, sport, fertility, travel, appearance and anxiety — the right choice depends on your priorities, not just the medical facts.
What are all my options?
Ask about waiting, monitoring, medicines, rehabilitation, a smaller or larger procedure, a different test, NHS referral, or a second opinion where that would help.
What would make me pause?
Active infection, pregnancy, unstable medical problems, smoking, medicines that increase bleeding, poor support at home, or feeling pressured are all reasons to slow down and get tailored advice.
What happens if I do nothing today?
For some problems, waiting is safe; for others, delay can make treatment harder. A good consultation should explain the trade-off in plain English.
Benefits
- Confirms AKI early, when many cases can still be reversed
- Identifies and treats the cause, such as dehydration, infection or a blockage
- Finds dangerous salt problems, especially a high potassium, that need urgent treatment
- Allows harmful medicines to be paused or adjusted to protect the kidneys
- Decides who can be safely monitored and who needs hospital care
Risks & complications
- Bruising or discomfort from blood tests
- Repeated blood tests to track whether kidney function is improving
- Uncertainty while the cause is worked out
- Temporarily pausing useful medicines while the kidneys recover
- Incidental findings on a kidney ultrasound that need follow-up
- Side effects of treatments used to manage a high potassium or fluid balance
- Needing admission when an outpatient plan turns out not to be safe
- A cause within the kidney that needs specialist tests
- A dangerously high potassium causing a serious heart rhythm problem
- Needing temporary dialysis if the kidneys fail badly
- A kidney biopsy and its small risks if a kidney disease is suspected
The main risks are missing a dangerously high potassium or a treatable blockage, and not recognising a medicine that is harming the kidneys. AKI is also a marker that something else is wrong (often dehydration or infection), so treating only the kidney numbers without finding the cause is a trap. Ask what your potassium is, what is thought to be causing the AKI, which of your medicines should be paused, and how often your bloods will be rechecked.
Published figures to discuss
Meaningful single percentages are difficult because AKI ranges from mild and quickly reversible to severe and life-threatening, and outcomes depend heavily on the cause, how early it is found, and the person's other health problems. Rates should be discussed individually rather than generalised.
| Figure | Reported range | How to interpret it | Source / confidence |
|---|---|---|---|
| Rapid kidney deterioration | Stage- and cause-dependent | NICE AKI guidance treats rising creatinine or low urine output as needing prompt cause-finding. | NICE NG148 — Acute kidney injury: prevention, detection and managementnice.org.ukSource-linked context |
| Hyperkalaemia causing arrhythmia | Emergency if severe or ECG changes present | Potassium must be checked and acted on urgently in significant AKI. | Guide sourcesClinical context |
| Medicine-related AKI missed | Common | NSAIDs, ACE inhibitors/ARBs during dehydration, diuretics, antibiotics and contrast can contribute. | NHS — Acute kidney injury (AKI)nhs.ukSource-linked context |
| Obstruction missed | Important reversible cause | Urinary retention, prostate disease, stones or pelvic cancer can cause AKI and may need bladder scan/ultrasound. | Guide sourcesClinical context |
These are literature figures, not a personalised prediction. Your own risks and likely benefits depend on your circumstances, your health, and how your care is carried out and followed up.
What happens afterwards
There is no physical recovery from the assessment itself. Afterwards, the focus is on treating the cause, watching the kidney blood tests recover, and reviewing which medicines to restart and when.
- Mild bruising from blood tests
- Needing several blood tests over a few days to track progress
- Feeling tired or run down from the underlying illness
- Gradual improvement in kidney numbers rather than an instant return to normal
Aftercare
- Keep up the fluid intake advised for you, unless you have been told to limit fluids.
- Do not restart paused medicines until your clinician confirms it is safe.
- Follow any 'sick day' advice about temporarily stopping certain medicines if you become unwell with vomiting, diarrhoea or fever.
- Attend the follow-up blood test that checks whether your kidneys have recovered.
- Tell any clinician about your recent AKI before you have contrast scans or start new medicines.
- Be cautious with anti-inflammatory painkillers, which can harm the kidneys, and ask before using them.
- Seek urgent help if you pass very little urine, become drowsy or breathless, or have palpitations.
- A complete, up-to-date medicines list, including painkillers and supplements
- A note of recent illness, fluid intake and urine output
- A record of any recent contrast scans or new medicines
- Details of long-term conditions such as diabetes or heart failure
- A written copy of your result, diagnosis and medication plan
- Clear instructions on which medicines are paused and when to restart
- The contact number for questions or worsening symptoms
Scars and how they heal
There are no surgical wounds. You may have a small bruise where blood is taken or a drip is placed. If a kidney biopsy is needed (uncommon), it leaves a small puncture mark in the skin over the back.
⚠ Get urgent help if…
- Passing very little or no urine — seek urgent help
- Becoming drowsy, confused or very weak — seek urgent help
- Breathlessness or swelling of the legs and around the eyes — seek urgent help
- Palpitations or a very slow or irregular heartbeat — call 999 (possible high potassium)
- Severe or worsening illness, high fever or signs of infection — seek urgent help
- Severe pain in the side or back, or being unable to pass urine — seek urgent help
Who to contact: your clinician, clinic or test provider first (keep their number to hand). For urgent advice when you can't reach them, call NHS 111. In an emergency, call 999.
General guidance — it doesn't replace the specific advice your specialist gives you.
Results & realistic expectations
A good outcome is when the cause is found and treated, the kidney blood tests recover towards their previous level, and dangerous salt problems are corrected. Many cases of AKI improve well when acted on early.
The results show how severe the AKI is and point to the cause, but a single set of numbers is a snapshot. Repeat tests over days are what show the direction of travel. Recovery to your previous baseline is not always complete, especially after severe AKI or in people with existing kidney problems, which is why follow-up testing matters.
Kidney function can recover fully after AKI, but an episode raises the chance of future kidney problems, so it is worth protecting your kidneys long term. A follow-up blood test confirms whether you have returned to your usual level. If you have ongoing kidney disease, you may need regular monitoring and a long-term plan with your GP or a kidney specialist.
Related tests, treatments or support
AKI assessment is often combined with treating the underlying problem — for example an assessment for dehydration and intravenous fluid therapy, or treatment of an infection that may need intravenous antibiotics. Electrolyte disturbances such as a high potassium are usually assessed and managed at the same time.
Follow-up & long-term care
You should have a follow-up blood test to confirm whether your kidneys have recovered, a clear plan on which medicines to restart and when, and advice on protecting your kidneys in future. People with severe AKI or underlying kidney disease may be referred to a kidney specialist.
- Attend follow-up blood tests until kidney function is confirmed stable
- Follow 'sick day' guidance on pausing certain medicines during illness
- Stay well hydrated unless advised otherwise, and be cautious with anti-inflammatory painkillers
- Tell clinicians about your AKI before contrast scans or new medicines
- If you have chronic kidney disease, keep to your monitoring plan
Repeat, follow-on and what comes next
- AKI is tracked with repeated blood tests; the picture and plan change as numbers move.
- Kidney function does not always return fully to baseline, especially after severe AKI.
- Paused medicines need a deliberate, reviewed decision before restarting.
- An episode of AKI raises the chance of future kidney problems and may need longer-term monitoring.
Ask what happens if the result is unclear or needs repeating, and what is included if further tests or follow-up are needed.
What good aftercare looks like
- A clear follow-up blood test to confirm whether kidney function has recovered.
- Explicit instructions on which medicines are paused and the plan to restart them.
- 'Sick day' guidance to protect the kidneys during future illness.
- A named contact and clear warning signs that mean seeking urgent help.
- Joined-up handover to the GP, and to a kidney specialist where needed.
What affects the cost
Costs vary a great deal between people and providers, and we don't publish prices. What matters is understanding what drives the cost and making sure your quote is complete. The main things that affect it:
- The length and complexity of the consultation and medicine review
- Blood tests and how often they need repeating to track recovery
- Urine tests and a kidney ultrasound if needed
- The reporting radiologist and how quickly results are needed
- Whether specialist kidney input or admission is required
- Follow-up appointments and repeat blood tests to confirm recovery
- The assessing clinician's fee and appointment length
- Blood tests, urine tests and any cannula or drip
- An ultrasound fee and the radiologist's reporting fee, if a scan is needed
- What happens, and what it costs, if you need admission or specialist care
- Repeat blood tests to confirm recovery
- Follow-up to review medicines and protect the kidneys
- A clear statement that severe AKI will be redirected to NHS emergency or hospital care
On the NHS? AKI is commonly detected and managed within NHS urgent and hospital care, often triggered automatically by blood-test alerts. Private same-day medicine may speed up assessment of a stable, lower-risk problem, but severe AKI is an emergency that belongs in hospital.
You're entitled to your total cost in writing — including reports, follow-up and what happens if the result is inconclusive — before you decide.
Consent traps and marketing red flags
These are not small details. They are often where patients lose choice, time to reflect, or realistic expectations.
Consent traps
- Not explaining that severe AKI or a high potassium needs emergency hospital care, not an outpatient plan.
- Treating blood results without explaining and treating the underlying cause.
- Not making clear which medicines are paused and when they will be reviewed.
- Not arranging or explaining the follow-up blood test that confirms recovery.
- Failing to give 'sick day' advice on pausing certain medicines during future illness.
Marketing red flags
- Selling 'kidney detox', cleanses or IV drips as treatment for or prevention of kidney injury.
- Offering routine kidney screening to well people as a way to 'catch' AKI.
- Downplaying the seriousness of a high potassium or severe AKI to keep care private.
- Implying an outpatient drip can treat significant kidney injury safely.
Choosing a specialist safely
- Check the specialist is on the GMC Specialist Register for this area.
- Make sure they work at a CQC-registered service, and look for membership of the relevant Royal College or professional body.
- You're entitled to time to consider and to have your questions answered before you agree — the specialist who looks after you should explain it, not a salesperson.
- Be wary of pressure: time-limited offers or deposits taken before you've had time to think are red flags, not bargains.
- You're entitled to your total cost in writing — including any follow-up — before you decide.
Questions to ask your medical professional
Take this to your consultation. A good specialist will welcome every one of these.
- What is causing my AKI, and how severe is it?
- What is my potassium level, and is it safe?
- Which of my medicines should be paused, and when can I restart them?
- How often will my blood tests be repeated to check recovery?
- Do I need a scan to rule out a blockage?
- What should I do if I become unwell again, and what are my warning signs?
- Are you on the GMC Specialist Register for this area, and which Royal College or professional body are you a member of?
- Will you be the specialist who carries out my test, and who looks after me afterwards?
- What are the risks for someone like me, and how often do your own patients have a problem or need it repeated or redone?
- What does a realistic result look like — and what can this test not achieve?
- What are my options, including waiting, doing nothing for now, or choosing a different approach?
- Can I have written information, results and aftercare instructions in a format I can use, including any accessibility or communication support I need?
- What is the total cost in writing, including any follow-ups, and how much time do I have to decide?
Frequently asked questions
What causes acute kidney injury most often?
Will I feel unwell if I have AKI?
Why do I need an ultrasound?
Why have some of my medicines been stopped?
Can AKI be reversed?
Is a high potassium dangerous?
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How we made this page
Medically reviewed by a GMC-registered consultant. Written in plain English, checked against NHS, NICE, GMC and relevant Royal College / specialist-society guidance, and kept under review. No clinic paid to appear on this page, and we publish no pricing. This is general information to help you prepare — it is not a substitute for advice from your own clinician. How we review our guides →
Source hierarchy: UK regulator and NHS/NICE guidance first, then relevant Royal College or specialist-society guidance, then peer-reviewed evidence for procedure-specific figures where available.
Sources & standards: NHS — Acute kidney injury (AKI) NICE NG148 — Acute kidney injury: prevention, detection and management NICE NG148 — full guideline (PDF) UK Kidney Association — Clinical practice guideline: management of hyperkalaemia in adults (2023) NICE QS76 — Acute kidney injury quality standard
Reviews reflect patients' experience of care, not clinical outcomes. For procedure volumes and outcome data see PHIN.
Last medically reviewed 2026-09-21. Spotted something wrong or out of date? Report an error in this guide.
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