Blood tests are a simple way to learn more about your kidneys. Test results can measure kidney function and help screen for signs of problems, including cancer.

A blood test alone can’t diagnose kidney cancer. But it can help doctors decide if more testing is needed. Here are some common blood tests and what their results can tell doctors about kidney cancer.

Complete Blood Count

A complete blood count (CBC) looks at the different types of cells in your blood. Aside from possible clues about cancer, a CBC can help your doctor determine if you’re in good shape for surgery.

CBC measures levels of red blood cells, white blood cells, and platelets. Here are some potential findings that may be related to kidney cancer.

Anemia

One of the most important findings on a CBC is anemia. Anemia means you have a low red blood cell count, which is common in many forms of cancer.

Healthy kidneys make a hormone called erythropoietin (EPO) that stimulates red blood cell production. One way kidney cancer may cause anemia is if it disrupts the production of EPO and levels drop too low.

If you have anemia, your doctor may order a separate blood test to see if it’s related to your EPO levels. Kidney damage is a possible cause of low EPO levels, so this can serve as another clue that something isn’t right with the kidneys.

High Levels of Red Blood Cells

Some forms of kidney cancer cause abnormally high red blood cell counts.

High Levels of White Blood Cells

White blood cell counts can also be higher than normal in some people with cancer. They’re a general sign that the immune system is working in high gear. Platelet levels may also be elevated.

Comprehensive Metabolic Panel

A comprehensive metabolic panel (CMP) measures 14 substances in your blood, including electrolytes and proteins. This test helps doctors assess the health of your kidneys and other organs.

Kidney Function Tests

Part of the metabolic panel includes specific tests for kidney function. The results can show impaired kidney function, which could be related to kidney disease or cancer.

Poor kidney function can also let doctors know that certain medications that stress the kidneys aren’t safe for you to take.

CMP tests kidney function by measuring:

• Creatinine — A waste product from your muscles that healthy kidneys filter out of the blood. High creatinine levels may mean your kidneys aren’t working as well as they should.
• Blood urea nitrogen (BUN) — BUN can be high when kidney function is impaired.

Together, these values help your care team understand how well your kidneys are working.

Liver Function Tests

Another portion of the CMP assesses liver function. Abnormal liver function isn’t a direct sign of kidney cancer. But if someone has kidney cancer, there’s a chance it could spread to the liver. If metastatic kidney cancer spreads to the liver, it may lead to problems with liver function.

Poor liver function can also affect the type of medication you can take. It’s important to know whether your liver isn’t working well so you can take steps to prevent further damage.

Liver function tests measure enzymes and proteins in your blood that reflect how well your liver is working.

These include substances like:

• Albumin — A protein made by the liver
• Bilirubin — Produced when red blood cells break down
• Liver enzymes — Including AST, ALT, and ALP
• Total protein — The amount of protein in your blood overall

Blood Calcium Levels

Calcium levels in the blood can be too high when people have kidney cancer. This condition is called hypercalcemia. Hypercalcemia can have serious impacts on how your muscles, nerves, and heart function.

High calcium can happen because some kidney tumors produce hormonelike substances that increase blood calcium levels. In some cases, it leads to sudden changes in mental status that require hospitalization.

Lactate Dehydrogenase

Lactate dehydrogenase (LDH) is an enzyme found in many tissues throughout the body. High levels can be a sign of tissue damage. Sometimes this is associated with kidney cancer.

LDH may also help predict how well someone with advanced kidney disease will respond to treatment. High LDH is associated with resistance to certain cancer drugs.

C-Reactive Protein

C-reactive protein (CRP) is a marker of inflammation. It’s not specific to cancer, but it has been linked to poor kidney function.

Your doctor may order a CRP test to assess your overall health. It’s a sign that the body is fighting a disease. CRP may be high because of kidney disease or other health conditions that can occur alongside kidney cancer and complicate treatment.

What Happens After an Abnormal Blood Test Result?

If blood test results or symptoms of kidney cancer raise concerns, the next step is usually imaging. These scans allow doctors to look directly at the kidneys and surrounding structures.

If imaging tests discover a suspicious growth, a biopsy (removing a tissue sample for examination) may be done to test for cancer cells. However, kidney cancer may sometimes be diagnosed with imaging alone.

Imaging

An ultrasound is often one of the first imaging tests used. Ultrasound testing doesn’t involve radiation and can detect masses in the kidney. An ultrasound uses sound waves to show if a growth is a solid tumor or fluid-filled. However, more imaging may be required to get the detailed image needed for a diagnosis of kidney cancer.

A computed tomography (CT scan) is commonly used to get a more detailed view. It can show the size, shape, extension, and location of a tumor, as well as whether it may have spread to nearby parts of the body.

In some cases, magnetic resonance imaging (MRI) may be used instead, especially if there are concerns about kidney function and the contrast dye used in CT scans.

Biopsy

If imaging shows a mass that looks like kidney cancer, a biopsy may or may not be needed. In many cases, doctors can make a treatment plan based on imaging alone, especially if surgery is planned.

However, a biopsy may be recommended if the diagnosis is unclear or if nonsurgical treatments are being considered.

Blood tests continue to play a role in the diagnosis and treatment of kidney cancer. They may be repeated to monitor changes and to prepare for procedures or treatments.

How Does Bloodwork Help Detect Kidney Cancer?

Blood tests and urinalysis (urine tests) are helpful ways to monitor your kidneys and screen for potential problems. Taking advantage of these screening tests can give you an early head start on any issues before they become a bigger threat to your health.

Equally important, they give your care team a clearer picture of your overall health. This information is essential when deciding on imaging, surgery, or other treatments.

By combining blood test results with imaging and, if needed, biopsy findings, doctors can make informed decisions about your care.

It’s normal to be nervous about any form of testing to look for kidney cancer. Asking your doctor to explain your results in plain language can help you better understand what they mean for you and what comes next.

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What lab tests have you had as part of cancer screening and monitoring? Let others know in the comments below.