nephritis blood test explained
Informed by recognized medical guidance
Overview
Nephritis is a condition where the kidneys become swollen and irritated. Blood tests help check how well your kidneys are working and look for signs of inflammation.
Key facts
- Nephritis means inflammation (swelling) of the tiny filters in your kidneys called glomeruli.
- Blood tests can measure waste products like creatinine and urea to see if your kidneys are filtering properly.
- Urine tests are also important to check for protein or blood that can leak when kidneys are inflamed.
Nephritis is not very common, but it can happen at any age. Some types are more common in children or young adults.
It can affect anyone, but certain types are more likely in people with autoimmune conditions (like lupus), after certain infections, or in those with a family history of kidney disease.
Symptoms
- Sudden inability to urinate (pass urine) for many hours
- Severe shortness of breath or chest pain
- Very high blood pressure (e.g., headache, vision changes, seizure)
- ⚠New or worsening swelling that makes it hard to breathe or move
- ⚠Urine that looks bright red or has large blood clots
- ⚠Flu-like symptoms that are getting worse (fever, chills, body aches)
Common symptoms
- Blood in your urine (pink, red, or cola-colored)
- Foamy or bubbly urine (sign of protein leak)
- Swelling in your face, hands, feet, or belly (edema)
- High blood pressure
- Fatigue or feeling very tired
Symptoms in children
- Blood in urine (often noticed after a sore throat or skin infection)
- Swelling around the eyes in the morning
- Less urine than usual, or dark urine
Symptoms in older adults
- Fluid buildup (swelling) in legs or belly
- Confusion or trouble concentrating (due to waste buildup)
- Shortness of breath (fluid in lungs)
Causes
Main causes
- Infections – such as strep throat, skin infections, or hepatitis
- Autoimmune diseases – when your immune system attacks your kidneys by mistake (e.g., lupus, IgA nephropathy)
- Medications – some drugs, including certain antibiotics and pain relievers, can cause a reaction
Risk factors
- Having a family history of kidney disease
- Having an autoimmune condition like lupus or vasculitis
- Recently having an infection (especially strep throat in children)
When to see a doctor
See a doctor urgently if:
- You notice blood in your urine (pink, red, or cola-colored)
- You have puffiness around your eyes or swelling in your hands or feet that appears suddenly
- Your urine output drops a lot, or you stop urinating
Book a routine appointment if:
- You have high blood pressure that is hard to control
- You have foamy urine for more than a few days
- You feel very tired for no reason, along with any of the above
Diagnosis
A doctor will review your symptoms, check your blood pressure, and order blood and urine tests. They may also use imaging or a kidney biopsy.
Tests that may be done
- Blood test: measures creatinine, blood urea nitrogen (BUN), and estimated glomerular filtration rate (eGFR) to see kidney function
- Urine test: checks for protein, blood, and infection markers
- Imaging: ultrasound or CT scan to look at kidney size and shape
- Kidney biopsy: a small sample of kidney tissue taken to look under a microscope – confirms the type of nephritis
What to expect at your appointment
The blood test is quick – a small blood sample from your arm. You may need to avoid eating or drinking for a few hours before some tests. Results usually come back in a day or two, and your doctor will explain what they mean.
Treatment
Treatment depends on the cause and severity of nephritis. The goal is to reduce inflammation, manage symptoms, and protect kidney function. Your healthcare team will create a plan tailored to you.
Self-care at home
- Stay hydrated: drink enough water unless your doctor advises otherwise
- Limit salt: too much salt can worsen swelling and blood pressure
- Avoid nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen – they can harm kidneys
- Monitor your blood pressure at home if advised
Medical treatments
Doctors may prescribe medications to lower blood pressure, reduce inflammation (like corticosteroids), or calm an overactive immune system. In some cases, medicines to remove extra fluid (diuretics) are used. Always follow your doctor’s instructions.
When is surgery considered?
Surgery is rarely needed for nephritis alone. If kidney failure occurs, dialysis or a kidney transplant may be considered. Your doctor will discuss these options if necessary.
Living with this condition
Living with nephritis often means regular checkups, taking prescribed medicines, and watching your diet. Many people manage well with treatment and lead full lives.
Lifestyle tips
- Take all medicines exactly as prescribed – don’t skip doses
- Check your weight daily – sudden gain can mean fluid buildup
- Avoid alcohol and tobacco – they stress the kidneys
- Get regular rest and manage stress
Diet and exercise
Your doctor or dietitian may recommend a low-salt, moderate-protein diet. Exercise is good, but avoid strenuous workouts if you feel very tired. Walking, swimming, and gentle yoga are often safe. Ask your healthcare team what’s right for you.
Mental health and emotional wellbeing
Dealing with a kidney condition can be stressful and worrying. It’s normal to feel anxious or down at times. Talk to your doctor or a counselor if you need support – you don’t have to face it alone.
Prevention
Not all types of nephritis can be prevented, but you can lower your risk by treating infections quickly, managing high blood pressure, and avoiding unnecessary medicines that can harm the kidneys.
Vaccines
Staying up to date on vaccines (like flu and pneumonia) can help prevent infections that might trigger nephritis. Ask your doctor which vaccines you need.
Screening programmes
If you have a family history of kidney disease or an autoimmune condition, your doctor may recommend regular blood and urine tests to catch kidney problems early.
Complications
If left untreated
- Chronic kidney disease (long-term damage that can get worse over time)
- High blood pressure that is hard to control
- Kidney failure (end-stage renal disease) requiring dialysis or transplant
Long-term outlook
With proper treatment, many people with nephritis recover fully or maintain good kidney function for years. Early detection and care give the best chance for a good outcome. Your healthcare team will help you manage the condition and maintain your quality of life.
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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.
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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 18, 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.