Understanding Chemotherapy

Chemotherapy (chemo) is a treatment for cancer. Chemo can be a single medicine. Or it can be a combination of medicines. Chemo can be used alone. Or it can be used along with surgery or radiation therapy. It can often shrink a tumor or prevent its spread.

Man in outpatient clinic having chemotherapy infusion.
Chemotherapy is often given in an outpatient setting. This means you don’t stay overnight in the hospital.

How chemotherapy works

Chemo kills cells that grow quickly. Many kinds of cancer cells grow fast. But many healthy cells grow fast, too. These include cells of the mouth, stomach lining, bone marrow, skin and hair. After chemo, these healthy cells are able to grow back. But the cancer cells die. That's why some chemo side effects get better with time. Side effects can include:

  • Hair loss

  • Upset stomach (nausea)

  • Low blood cell counts


Usually, chemo is given in cycles of treatment. A cycle is the time from 1 cancer treatment to the next. For instance, a 3-week cycle may be treatment given 2 weeks in a row, and then 1 week off. A 3-week cycle may also be treatment given once every 3 weeks. Time is needed between treatments during the cycle. This lets normal cells recover before the next treatment.

The goals of chemotherapy

Chemo can kill cancer cells. As a result, it may do the following:

  • Shrink cancer before surgery. This is called neoadjuvent care.

  • Kill cancer cells that may remain after surgery. This is called adjuvent care.

  • Reduce symptoms such as pain. This is called palliative care.

  • Control cancer for a period of time. This is also a kind of palliative care.

  • Cause remission. This means there is no sign of the cancer on medical tests.

  • Cure the cancer. This means there is no sign of the cancer years after treatment.

Side effects of chemotherapy

Because healthy cells are also damaged with chemo, you may have side effects such as:

  • Nausea and vomiting

  • Appetite changes

  • Hair loss

  • Low red blood cell count (anemia)

  • Infections

  • Bleeding

  • Mouth and throat sores

  • Weight changes

  • Skin changes such as dry skin, itching, and acne

  • Lack of interest in sex

  • Severe tiredness (fatigue)

  • Trouble remembering and focusing

  • Stress and depression

  • Constipation or diarrhea

Long-term risks

There are some long-term risks with chemo. But the benefits usually outweigh the risks. Risks depend on the type of chemo used. Some possible long-term risks include:

  • Being unable to have children (infertility)

  • Damage to some organs, such as the heart, kidneys, liver, or lungs

  • Lasting nerve damage

  • Another cancer growing at a later time

Online Medical Reviewer: L Renee Watson MSN RN
Online Medical Reviewer: Raymond Turley Jr PA-C
Online Medical Reviewer: Todd Gersten MD
Date Last Reviewed: 10/1/2021
© 2000-2023 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.