Understanding Your Lab Test Results

When you have cancer, you will probably need regular lab, imaging, or other tests. Blood tests are done to help watch your body’s response to treatment. They can show small changes before problems get serious. Keeping track of your lab results lets your doctor take action as soon as your blood counts change to help prevent many cancer-related problems and cancer treatment side effects. The two most common types of lab tests are the complete blood count (CBC) and the chemistry panel or metabolic profile.

Getting your lab test results

Some people find it helps to ask for a copy of their lab results and have a member of their cancer care team go over the numbers with them. Different labs can have different normal ranges for blood tests. By getting a copy of your test results, you can see what the normal ranges are for the lab that tested your blood and where your numbers fall within that range.

The Office of the National Coordinator for Health Information Technology (ONC) enacted the Cures Act. The Cures Act is intended to make it easier for people to be able to see their medical records, clinical notes, and their costs of care. But, it doesn't always allow health care providers to delay the release of health information to patients, including lab, imaging, pathology, and other test results. This means that patients may see their results on a patient portal at the same time as their health care provider or before their health care provider has had a chance to review and explain them. 

Sometimes, you might see your lab test results before you have a chance talk about what they mean with your health care team. This can cause worry, especially if the results are unclear or seem to show something abnormal. Talking to the health care provider who is ordering the tests ahead of time might help. Here are some things you might ask about:

• What results you might expect, where you can get them, and when they might be available
• What a normal or abnormal result is and what it might mean for you
• When and how they will contact you to discuss your results
• Who to call if you see results first and have concerns about them

Complete blood count (CBC)

The most common lab test that you’ll have done during treatment is called a complete blood count, or CBC. Blood is made up of water, proteins, nutrients, and living cells. A CBC tells your cancer care team about the cells in your blood. It measures 3 basic types of blood cells:

• Red blood cells
• White blood cells
• Platelets

Each of these cells has a special purpose. And each can be harmed by cancer and cancer treatments.

Red blood cells (RBCs)

RBCs carry oxygen to and carbon dioxide away from the cells in your body. The normal range for RBCs is between 4.2 and 6.1 million/mcL (4.2-5.4 million/mcL for women and 4.7-6.1 million/mcL for men).

The CBC measures red blood cells in many ways. On your lab report, you might also see values for:

• Hemoglobin (Hgb), the part of each RBC that carries iron (the normal range is 12-18 g/dL)
• Hematocrit (Hct), the percent of RBCs in the blood (the normal range is 37-52%)

When the Hgb and Hct values fall too low, it’s called anemia. When you have anemia, your body is not able to get enough oxygen to all of your cells. This can cause a fast heart beat, tiredness (fatigue), trouble breathing, and other symptoms.

White blood cells (WBCs)

WBCs fight infection. There are many types of white blood cells and each fights infection in a special way.

The most important infection-fighting WBC is the neutrophil. The number doctors look at is called your absolute neutrophil count (ANC). For a healthy person, the normal range for an ANC is between 2,500 and 6,000.

The ANC is found by multiplying the WBC count by the percent of neutrophils in the blood. For instance, if the WBC count is 8,000 and 50% of the WBCs are neutrophils, the ANC is 4,000 (8,000 × 0.50 = 4,000).

When the ANC drops below 1,000 it is called neutropenia. Your doctor will watch your ANC closely because the risk of infection is much higher when the ANC is below 500.

A low WBC count increases the risk of infection, but a high WBC count can be a sign that your body is fighting an infection.

Platelets (Plts)

Platelets help control bleeding. You may bruise or bleed easily when your platelet levels are low. The risk of bleeding goes up when platelet levels drop below 20,000.

When your platelet count is low, your health care team may call it thrombocytopenia.

Chemistry panel (metabolic profile)

Another type of blood test looks at blood chemistry. Chemistry panels may also be called by other names, such as metabolic profile or blood chemistry profile. One blood sample can be used to measure many things like:

• Fats (lipids)
• Proteins
• Sugar (glucose)
• Electrolytes (like potassium, magnesium, sodium, and calcium)
• Enzymes

Certain blood chemistry tests can show how well your organs are working. For instance, liver function studies tell your doctor how well your liver is working. Other tests look at how well your kidneys are working. The chemistry panel may also show other problems with body function.

Some treatments can cause changes in your body’s blood chemistry, such as a drop in the amount of potassium in your blood. Your blood chemistry balance can also be changed by dehydration (not enough fluid in the body), which may be caused by nausea, vomiting, or diarrhea. Your doctor will do blood chemistry tests if there’s concern that you may have any of these problems.

If the tests show that certain electrolytes are too low, your doctor may decide to replace them. If the tests show you are dehydrated, you may be given intravenous (IV) fluids. It’s important to get the tests your doctor wants because most of the time you won’t have any symptoms until one or more blood chemistry values are dangerously low or high.

How to find the normal range for a CBC or chemistry panel

Each lab has its own range for what it considers normal values for complete blood counts and chemistry panel results. The range of normal values might be called the reference range. What’s normal for one lab might not quite be normal for another, so it’s important to know what your lab’s normal range is when looking at your results. Normal ranges for some tests also vary by age and sex. On most lab reports the normal ranges for each test and a notation telling you if yours is high or low are printed on the lab report, next to your test results.

Common terms and normal values on a CBC report