Cystatin C test
Informed by recognized medical guidance
Overview
The cystatin C test is a blood test that measures a protein called cystatin C. Your body makes this protein, and healthy kidneys remove it from your blood. When the kidneys are not working well, the level of cystatin C rises. This test gives your doctor a more accurate picture of your kidney function than some other tests, especially in certain situations.
Key facts
- Cystatin C levels are not affected by your muscle mass, so the test can be more accurate for older adults, people with muscle wasting, or those on special diets.
- The test is often used together with a creatinine test to confirm or clarify how well your kidneys are filtering waste.
- Results from the cystatin C test help your doctor diagnose chronic kidney disease (CKD) and decide on the best treatment plan.
The cystatin C test is becoming more common, especially for people whose creatinine tests may not be reliable, such as those with diabetes, heart failure, or after a kidney transplant.
It is used for anyone who needs a precise check of kidney function, including older adults, people with long-term conditions like high blood pressure or diabetes, and those who have had a kidney transplant.
Symptoms
- Sudden, severe shortness of breath or trouble breathing
- Chest pain or pressure
- Confusion or loss of consciousness
- ⚠A sudden drop in urine output (very little or no urine for several hours)
- ⚠Severe swelling that makes it hard to breathe or move
- ⚠Very high blood pressure (180/120 mm Hg or higher) that does not come down
Common symptoms
- Feeling very tired or weak
- Swelling in your ankles, feet, or hands (oedema)
- Changes in how much you urinate – either more or less than usual
- Blood in your urine
- High blood pressure that is hard to control
Symptoms in children
- Poor growth or not gaining weight as expected
- Frequent urination, especially at night (bedwetting that is new or worse)
- Puffiness around the eyes
Symptoms in older adults
- Confusion or trouble thinking clearly
- Loss of appetite and weight loss
- Itchy, dry skin
- More frequent infections
Causes
Main causes
- Diabetes – high blood sugar can slowly damage the tiny filters in your kidneys.
- High blood pressure – constant high pressure strains the blood vessels in the kidneys.
- Glomerulonephritis – inflammation of the kidney's filtering units, often from an infection or autoimmune condition.
Risk factors
- Family history of kidney disease
- Being over 60 years old
- Obesity
- Smoking
- Long-term use of non‑prescription painkillers (ask your doctor if this applies to you)
When to see a doctor
See a doctor urgently if:
- If you have sudden swelling in your legs or face, blood in your urine, or a big change in urination.
- If you have severe high blood pressure symptoms like a bad headache, vision changes, or nosebleeds.
Book a routine appointment if:
- If you have diabetes or high blood pressure, get your kidney function checked regularly as your doctor advises.
- If you are over 60 and have other risk factors, ask about a kidney check.
Diagnosis
To check for kidney disease, your doctor will take your medical history, do a physical exam, and order blood and urine tests. The cystatin C test is one of the blood tests used to measure how well your kidneys filter waste.
Tests that may be done
- Cystatin C blood test
- Creatinine blood test
- Urine test for protein (albumin)
- Imaging tests like an ultrasound of the kidneys
What to expect at your appointment
A small sample of blood is taken from a vein in your arm. You do not need to fast or stop your medicines unless your doctor tells you. Results usually take a few days. Your doctor will explain what the number means for your kidney health and what to do next.
Treatment
Treatment for chronic kidney disease (CKD) focuses on slowing down the loss of kidney function and managing related health problems. The plan depends on the stage of CKD and the cause.
Self-care at home
- Monitor your blood pressure at home if advised by your doctor.
- Take all medications exactly as prescribed.
- Avoid smoking and limit alcohol.
- Manage your diabetes carefully if you have it.
Medical treatments
Your doctor may prescribe medications to lower blood pressure, control blood sugar, reduce cholesterol, or protect your kidneys. They will also adjust the doses of any medicines that are cleared by your kidneys. Always talk to your doctor before starting or stopping any medication.
When is surgery considered?
If kidney disease reaches an advanced stage, treatments such as dialysis or a kidney transplant may be needed. Your healthcare team will discuss these options with you if they become necessary.
Living with this condition
Living with chronic kidney disease means staying on top of your check‑ups and following your treatment plan. Many people with early‑stage CKD can continue their daily activities and enjoy a good quality of life.
Lifestyle tips
- Quit smoking – it helps protect your kidneys and heart.
- Limit salt to help control blood pressure.
- Stay active with moderate exercise like walking or swimming.
- Avoid high‑dose or frequent use of non‑prescription painkillers (such as ibuprofen or similar).
Diet and exercise
A kidney‑friendly diet often means eating less salt, protein, and certain minerals like potassium and phosphorus. A dietitian can create a meal plan that works for you. Exercise helps maintain a healthy weight and lower blood pressure. Aim for 30 minutes of activity most days, but check with your doctor first.
Mental health and emotional wellbeing
Living with a long‑term condition can be stressful. It is normal to feel worried, sad, or frustrated at times. Talk to your doctor or a counsellor if these feelings last more than a couple of weeks.
Prevention
Chronic kidney disease cannot always be prevented, but you can lower your risk by keeping diabetes and high blood pressure under control, eating a healthy diet, not smoking, and maintaining a healthy weight.
Vaccines
Get flu and pneumonia vaccines as recommended by your doctor. Infections can put extra strain on your kidneys.
Screening programmes
If you have diabetes, high blood pressure, or a family history of kidney disease, ask your doctor about regular kidney function tests, including the cystatin C test.
Complications
If left untreated
- Anaemia (low red blood cells, causing tiredness and weakness)
- Weakened bones (from mineral imbalances)
- High potassium levels (can be dangerous for the heart)
- Fluid buildup in the lungs (causing shortness of breath)
- Heart disease
Long-term outlook
With early diagnosis and proper management, many people with chronic kidney disease can maintain a good quality of life for many years. The cystatin C test helps your doctor monitor your kidneys closely and adjust treatment as needed. Even if kidney disease progresses, treatments like dialysis and transplant are available and can help you continue living well.
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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 16, 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.
Guidance may differ by country or region. Confirm local recommendations with a qualified healthcare provider.