kidney flare ups
Informed by recognized medical guidance
Overview
A kidney flare-up is a sudden episode where your kidneys do not work as well as they normally do. This can happen quickly over hours or days, and it may cause symptoms like swelling, tiredness, or less urine. In many cases, it is a temporary setback, but it should be checked and treated early.
Key facts
- Kidney flare-ups often happen in people who already have chronic kidney disease.
- Dehydration, infections, and certain medicines can trigger a flare-up.
- Early care can help protect your kidney function and improve recovery.
Kidney problems are common, and a sudden flare-up is a major reason people with kidney disease go to the hospital. It can also happen to someone who did not know they had kidney problems.
Anyone can have a kidney flare-up, but you are more at risk if you are older, have diabetes or high blood pressure, have heart disease, or already have chronic kidney disease.
Symptoms
- No urine for several hours or very little urine
- Trouble breathing or chest pain
- Convulsions or seizures
- Fainting or loss of consciousness
- Sudden confusion
- ⚠High fever with shaking chills or pain in your back or side
- ⚠Repeated vomiting that prevents you from keeping fluids down
- ⚠Severe swelling that gets worse quickly
- ⚠Blood in your urine
- ⚠Any sudden, severe symptom that does not feel like your usual kidney flare-up
Common symptoms
- Swelling in your feet, ankles, or hands
- Being more tired than usual
- Feeling sick or vomiting
- Passing less urine than normal
- Urine that looks foamy, cloudy, or has blood
- Pain in your lower back or side
- Shortness of breath
- Confusion or difficulty thinking clearly
Symptoms in children
- Swelling around the eyes, face, or legs
- Poor appetite or not feeding well
- Bedwetting when they were previously dry
- Being unusually sleepy, fussy, or irritable
- Fever with back pain
Symptoms in older adults
- Feeling unusually weak or confused
- Loss of appetite and reduced fluid intake
- Swelling in the legs or hands
- Suddenly passing less urine
- Nausea or abdominal discomfort
Causes
Main causes
- Not drinking enough fluids (dehydration)
- Urinary tract or kidney infection
- A blocked bladder or kidney, such as from a kidney stone
- Certain medicines, especially some painkillers, blood pressure pills, or antibiotics – always check with your doctor
- Sudden poor control of blood pressure or blood sugar
- A flare-up of an autoimmune condition, such as lupus
Risk factors
- Chronic kidney disease
- Diabetes or high blood pressure
- Heart failure or liver disease
- Age 65 or older
- Recent hospital stay or severe illness
- Using medicines that can affect the kidneys
- Drinking too little, especially in hot weather or when older
When to see a doctor
See a doctor urgently if:
- Sudden change in urine output, swelling, or breathlessness
- Fever with back or side pain
- Repeated vomiting or confusion
Book a routine appointment if:
- You have kidney disease and notice your usual symptoms getting worse slowly
- You have new swelling, fatigue, or appetite changes that last more than a few days
Diagnosis
Your doctor will ask about your symptoms and health history, check your blood pressure, and feel for swelling or tenderness. They will then usually order blood and urine tests.
Tests that may be done
- Blood test to check creatinine and eGFR, a measure of kidney filtering
- Urine test to check for blood, protein, or infection
- An ultrasound scan to look at the kidneys and bladder
- Blood pressure measurement
- Sometimes a small sample of kidney tissue, called a biopsy, if needed
What to expect at your appointment
Some results are ready the same day. Depending on the findings, you may be treated at home, in an urgent care clinic, or in hospital. A kidney specialist may be involved if your flare-up is severe or your kidney function does not improve.
Treatment
Treatment depends on what is causing the flare-up and how severe it is. The goal is to remove the trigger, ease your symptoms, and keep your kidney function as stable as possible.
Self-care at home
- Stay hydrated, but do not exceed the fluid amount your doctor or nurse tells you if they have set a limit
- Rest while symptoms are active
- Follow any dietary advice, such as reducing salt
- Avoid alcohol and smoking
- Monitor your urine output and keep a simple diary if it helps
- Do not take any new medicines or supplements without asking your care team
Medical treatments
Your doctor may adjust your current medicines, treat an infection with the right antibiotic, or give you fluids through a drip in hospital. They may also treat high blood pressure or high blood potassium. Do not start or stop any medicine without talking to your healthcare professional.
Living with this condition
Learn your own warning signs. If you have kidney disease, ask your care team what a flare-up might look like for you and what to do when it happens. Not every day will be bad; most people manage kidney conditions with the right support.
Lifestyle tips
- Take medicines exactly as prescribed, even when you feel well
- Keep blood pressure and blood sugar in a target range you agree with your doctor
- Stay active with gentle movement, such as walking, if you feel able
- Get enough sleep and manage stress in ways that work for you
- Avoid smoking and limit alcohol
Diet and exercise
Your diet may need to change if your kidney function is lower. A renal dietitian can help you adjust salt, potassium, phosphorus, and protein safely. Choose gentle exercise like walking or swimming, and ask your team before starting a new routine.
Mental health and emotional wellbeing
Living with the fear of a kidney flare-up can be stressful. Some people feel anxious, frustrated, or low. These feelings are valid. Talk to a trusted friend, family member, or your doctor, and ask about counselling or self-help resources if you need more support.
Prevention
You cannot always prevent a kidney flare-up, but you can reduce your risk by staying well-hydrated, avoiding harmful medicines, controlling blood pressure and blood sugar, and getting early treatment for infections.
Vaccines
Recommended vaccines, including flu and COVID-19, can lower your chance of serious infections that might trigger a kidney flare-up. Talk to your healthcare professional about which vaccines you should have.
Screening programmes
If you have risk factors such as diabetes or high blood pressure, regular kidney blood and urine tests can help catch problems early.
Complications
If left untreated
- Permanent loss of kidney function
- Fluid build-up in the body, causing severe swelling or breathing difficulty
- High potassium levels, which can disturb the heartbeat
- Anaemia, a shortage of red blood cells causing tiredness
- Later, kidney failure needing dialysis or a transplant
Long-term outlook
With early treatment, many kidney flare-ups improve and kidney function can return to its usual level. The outlook is better when you get help quickly and work with your healthcare team. If flare-ups happen again, your team can help you create a plan to protect your kidneys as much as possible.
Find support
International organisations
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Always verify with your doctor
Health guidelines vary by country and region. The information in this article is based on international clinical guidelines but may not reflect the specific guidelines, medications, or practices in your country. Always discuss your health concerns with your own doctor or healthcare provider, and refer to your local national health guidelines where available.
Important notice This information is for educational purposes only. It does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider about your specific situation. If you are experiencing a medical emergency, call your local emergency services immediately.
Related conditions
Sources and guidance
This article is educational and is prepared with reference to recognized health information and clinical guidance sources where available. Specific source links may vary by topic.
Last updated: July 31, 2026
Educational note: This information is for education only and is not a diagnosis.
Use it to support, not replace, advice from a licensed clinician.
If symptoms are severe, worsening, or urgent, call your local emergency number or seek emergency care.