Your doctor may monitor your blood cell counts carefully during your cancer treatment. There's a good reason you're having your blood drawn so often — low blood cell counts put you at risk of dangerous complications. Find out what your doctor is looking for and why it's so important to be vigilant for low blood cell counts. Know what you should be on the look out for, too.

When your doctor looks at your blood cell counts, he or she is looking at your levels of:

• White blood cells. These cells help your body fight infection. A low white blood cell count (leukopenia) can lead to infection, a dangerous and sometimes deadly complication of cancer treatment.
• Red blood cells. Red blood cells carry oxygen throughout your body. Your red blood cells' ability to carry oxygen is measured by the amount of hemoglobin in your blood. If your level of hemoglobin is low, you're anemic and your body works much harder to supply oxygen to your tissues. This can make you feel fatigued and short of breath.
• Platelets. Platelets help your blood clot. A low platelet count (thrombocytopenia) means your body can't stop itself from bleeding, which could lead to dangerous blood loss.

If you're undergoing certain cancer treatments that could cause low blood cell counts, your doctor will likely monitor your blood cell counts regularly using a test called a complete blood count (CBC). Low blood cell counts are detected by examining a blood sample taken from a vein in your arm.

Cancer-related causes of low blood cell counts include:

• Chemotherapy. Certain chemotherapy drugs can damage your bone marrow — the spongy material found in your bones. Your bone marrow makes blood cells. When it's damaged, your bone marrow doesn't produce as many blood cells and your blood counts drop. Your doctor can tell you whether your specific chemotherapy treatment and dose will put you at risk of low blood cell counts.
• Radiation therapy. If you receive radiation therapy to large areas of your body and especially to the large bones that contain the most bone marrow, such as your pelvis, legs and torso, you might experience low levels of red and white blood cells. Radiation therapy is less likely to have a significant effect on your platelet count. Radiation combined with chemotherapy increases your risk of low blood cell counts.
• Cancers of the blood and bone marrow. Blood and bone marrow cancers, such as leukemia, attack different parts of your bone marrow. The cancerous cells can displace other cells in your bone marrow, making it difficult for your bone marrow to produce the blood cells your body needs.
• Cancers that spread (metastasize). Cancer cells that break off from a tumor can spread to other parts of your body, including your bone marrow. Some examples of cancers that could spread to your bone marrow include breast cancer, lung cancer and prostate cancer. This is an unusual cause of low blood counts.

Low blood cell counts can lead to very serious complications that at best will delay your next round of treatment and at worst can kill you. Monitoring your blood counts allows your doctor to prevent any complications.

The most serious complications of low blood cell counts include:

• Infection. With a low white blood cell count and, in particular, a low level of neutrophils (neutropenia), a type of white blood cell that fights intruders, you're at higher risk of developing an infection. If you develop an infection when you have a low white blood cell count, your body can't protect itself from the infection. Even a mild infection can delay your chemotherapy treatment, since your doctor may wait until your infection is eradicated and your blood counts go back up before you continue. At times your doctor may choose to lower the dose of chemotherapy you receive in order to decrease your chance of developing serious low white blood cell counts.
• Anemia. A low red blood cell count is anemia. The most common symptoms of anemia are fatigue and shortness of breath. In some cases fatigue becomes so severe that you must temporarily halt your treatment or reduce the dose you receive. Anemia can be relieved with a blood transfusion or with medication to increase your body's production of red blood cells.
• Bleeding. Low numbers of platelets in your blood can cause bleeding, sometimes for no reason. You might bleed excessively from a small cut or bleed spontaneously from your nose or gums. A low platelet count can delay your treatment. You may have to wait until your platelet levels go up in order to continue with chemotherapy or to have surgery.

Unless your blood cell counts are very low, you probably won't experience any signs or symptoms and you won't be able to tell that your blood counts are down. That's why your doctor will order frequent blood tests to track your blood cell counts.

Ask your doctor whether your cancer treatment is likely to cause low blood cell counts and what signs and symptoms you should be looking for. If you notice any signs or symptoms of low blood cell counts, tell your doctor right away.

If you have low blood cell counts, your treatment will depend on which counts are low and what's causing the low numbers. Common treatments include:

• Blood transfusions. Transfusions help people with low levels of red blood cells and platelets. In a blood transfusion you're given either red blood cells or platelets from people who've donated blood.
• Medications. Your doctor may prescribe medications that encourage your body to produce more blood cells. Medications are also used to prevent low blood cell counts in people who have a high probability of experiencing complications of cancer treatment.
• Stopping treatment. In severe cases you may need to delay your cancer treatment until your blood cell counts rise.

What type of treatment you receive depends on your cancer treatment and your own body. Though medications will help some people with low blood cell counts, other people won't recover as quickly and may need to stop treatment in order to raise blood cell counts faster.

Take steps to keep your body healthy when you have low blood cell counts. For instance:

• Eat a balanced diet. Your body will need all the vitamins and nutrients it can get to heal itself during and after your treatment. Eat plenty of fruits and vegetables. If treatment complications make eating difficult — for example, if you experience nausea and vomiting or mouth sores — experiment to find foods you can tolerate.
• Avoid injury. Many everyday activities put you at risk of cuts and scrapes. A low platelet count makes even minor abrasions serious. A low white blood cell count can turn a small cut into a starting point for a dangerous infection. Use an electric shaver rather than a razor to avoid nicks. Ask someone else to cut up food in the kitchen. Be gentle when brushing your teeth and blowing your nose.
• Avoid germs. It's impossible to avoid all germs, but avoid unnecessary exposure when you can. Wash your hands frequently. Avoid people who are sick and stay away from crowds. Have someone else clean the litter box, bird cage or fish tank. Don't eat raw meat or eggs.
• Rest. If you feel tired, stop and rest. Your body is working hard to fight the cancer cells and heal the healthy cells damaged by your treatment. Don't feel guilty about taking time for yourself and asking others to help you. Plan your most important activities for the time of day when you feel most energetic.

Talk to your health care team about other ways you can cope with low blood cell counts.