Side effects of chemotherapy

Chemotherapy drugs kill cancer cells, but they can also damage healthy cells. Damage to healthy cells causes side effects. Different cells and tissues in the body cope differently with chemotherapy. Chemotherapy drugs affect cells that are actively growing and dividing, such as blood cells in the bone marrow, cells lining the mouth and gastrointestinal (GI) tract and hair follicle cells.

Side effects can happen with any type of treatment, but not everyone has them or experiences them in the same way. If you develop side effects, they can happen any time during, immediately after or a few days or weeks after chemotherapy. Sometimes late side effects develop months or years after chemotherapy. Most side effects go away on their own or can be treated, but some side effects may last a long time or become permanent.

You may worry about the side effects of chemotherapy. But many types of chemotherapy given today are easier to tolerate than they were in the past. And your healthcare team is there to help prevent side effects and help you treat them. Side effects of chemotherapy will depend mainly on the type of drug, the dose, how it’s given and your overall health.

The following are the most common side effects that people tend to experience with chemotherapy. Tell your healthcare team if you have these side effects or others you think might be from chemotherapy. The sooner you tell them of any problems, the sooner they can suggest ways to help you deal with them.

Low blood cell counts

Low blood cell counts happen because of chemotherapy’s effect on blood cells made in the bone marrow. Blood cell counts often reach their lowest level about 7 to 14 days after chemotherapy. Low blood cell counts is the most common and most serious side effect of chemotherapy. When it happens, the dose of chemotherapy is adjusted right away or chemotherapy may have to be stopped temporarily.


Fatigue makes a person feel more tired than usual and can interfere with daily activities and sleep. Fatigue may be caused by anemia, specific chemotherapy drugs, poor appetite or depression. It may also be related to toxic substances that are made in the body when cancer cells break down and die. Fatigue can happen within days after a chemotherapy treatment and can last long after treatment ends. It also tends to be worse when you are having other treatments, such as radiation therapy. Fatigue usually gets better over time.

Nausea and vomiting

Nausea and vomiting can start within the first few hours after chemotherapy drugs are given and usually last about 24 hours. However, nausea and vomiting may start more than 24 hours after treatment and last several days (called delayed nausea and vomiting). Some people may have anticipatory nausea after having a few treatments, where they feel nauseated even before treatment is given because they expect to be sick. The healthcare team can help you manage nausea and vomiting by prescribing antinausea drugs.

Not all chemotherapy drugs cause nausea and vomiting. Nausea and vomiting are more likely when combinations of chemotherapy drugs are given.

Loss of appetite

Nausea and vomiting, fatigue or a buildup of waste products as cancer cells die can cause a loss of appetite. Some chemotherapy drugs can cause temporary changes in taste and smell, which can make food less appetizing. Some people may not feel like eating at all, even though they know they need to. This can lead to weight loss and malnutrition. Having good nutrition during and after chemotherapy is important to help you recover from treatment.

Hair loss

Hair loss (alopecia) is a common side effect of many, but not all, chemotherapy drugs. Hair follicles are damaged by chemotherapy because the drugs affect cells that are growing quickly. It’s hard to predict how much hair you will lose and how long hair loss will last because it depends on the type and dose of drugs used as well as your body. Hair loss can happen on any part of the body, not just your head. You may begin to lose hair within a few days or 2 to 3 weeks after chemotherapy starts. Hair usually grows back once you finish chemotherapy.


Diarrhea is the frequent passing of loose, watery stools. It happens because chemotherapy drugs often affect the cells that line the gastrointestinal (GI) tract. Many factors increase the risk of diarrhea, including the type and dose of chemotherapy. Diarrhea is often worse when combinations of chemotherapy drugs are given. Diarrhea can happen soon after chemotherapy starts and may continue for up to 2 weeks after treatment has ended.


Constipation is when stools become hard, dry and difficult to pass. Constipation can happen for a number of reasons including the type of chemotherapy drug used, medicines given with chemotherapy to relieve nausea and vomiting, and drinking less fluids. Constipation tends to happen within a few days after chemotherapy starts.

Sore mouth

A sore mouth (also called stomatitis or oral mucositis) happens because of chemotherapy’s effect on cells inside the mouth. Many drugs can cause a sore mouth, but it happens more often when higher doses of drugs are used. Your mouth may become sore anywhere from 5 to 10 days after chemotherapy starts. It often gets better on its own a few weeks after treatment is finished.

You may develop painful sores, ulcers or infection in the mouth, throat or gums. Regular mouth care can help prevent a sore mouth and lower the chance of infection. The healthcare team will tell you how often to clean and rinse your mouth and what to use. Some people may need to take pain medicines.

Inflamed mucous membranes

Mucous membranes line many of the organs in the body, from the mouth to the rectum and vagina. Chemotherapy can damage cells in the mucous membrane so they become inflamed (a condition called mucositis). This can lead to painful ulcers, bleeding and infection. Mucositis is usually temporary and goes away a few weeks after treatment.

Difficult or painful swallowing, heartburn or pain in the upper abdomen should be reported to the doctor or healthcare team. Pain caused by an inflamed esophagus (called esophagitis) can affect eating. You may need to change what you eat or take pain-relieving medicines if you have trouble swallowing or it hurts to swallow.

Report vaginal itching, discharge, odour, pain and bleeding to the doctor or healthcare team. Use cool compresses or a warm water bath to help relieve vaginal itching and pain. Avoid using scented tampons and feminine hygiene pads. If you develop a vaginal infection or have severe pain, your doctor may prescribe medicines to help.

Changes in taste and smell

Some chemotherapy drugs can affect taste buds causing changes in taste. For example, you may find that meats have a metallic taste. Even foods that you normally crave, such as sweet or salty snacks, can taste bad. You may become more sensitive to smells. Smells that others don’t notice may make you nauseous. It can take months for both the sense of smell and taste to return to normal after chemotherapy.

Skin changes

Some drugs can cause skin problems or skin irritation. Skin changes can happen during and for some time after chemotherapy. Skin reactions can include redness, itching, dryness, rash or nail changes.

Skin may also be more sensitive to or easily irritated by the sun during chemotherapy treatment.

Eye changes

Some chemotherapy drugs cause eye changes, such as blurry vision, watery eyes and trouble wearing contact lenses. Tell the doctor or healthcare team if you have changes to your eyes.


Some chemotherapy drugs can cause painful side effects, such as aching in the muscles and joints, headaches and stomach pains. Pain may be felt as burning, numbness, tingling or shooting pains in the hands and feet (called peripheral nerve damage). This type of pain can last long after treatment ends. The healthcare team will tell you what medicines to use to relieve the pain.

Pain at the injection site

Many chemotherapy drugs are given by an injection, usually into a vein (intravenously, IV). Getting the needle or catheter into the vein may cause some discomfort or pain. But you probably won’t feel any pain or discomfort when the IV chemotherapy drugs are given.

There is a small risk that chemotherapy drugs will escape from the vein and leak into the surrounding tissues. This is called extravasation. Some chemotherapy drugs irritate tissues. These drugs are called vesicants. In some cases, chemotherapy drugs that escape from the vein can cause severe damage to the skin and surrounding soft tissue. Your healthcare team will monitor you for signs of extravasation. Tell your healthcare team if you develop redness, swelling, pain, burning or stinging at the injection site.

Inflamed vein

An intravenous (IV) needle or catheter can cause the vein to become inflamed (a condition called phlebitis). The area around the insertion site or along the vein can become red, warm, tender or painful and swollen. The chances of developing phlebitis increase with the:

  • length of time the IV needle or catheter is in place
  • type of drug or solution being given
  • size and location of the needle or catheter

Nurses often check IV sites for signs of phlebitis. If phlebitis occurs, the IV needle or catheter is usually removed and placed in another area. You may be given warm, moist compresses to help reduce inflammation.

Hearing problems

Some types of chemotherapy drugs can damage the inner ear, which can cause hearing loss or balance changes. This usually goes away after treatment has ended, but your doctor may lower the dose of chemotherapy or change your treatment to prevent further damage to hearing.

Organ damage

Some chemotherapy drugs can cause organ damage. The healthcare team takes steps to limit the damage to healthy cells, but organ damage can happen. Some of the organs that may be affected by chemotherapy include the:

Some types of organ damage develop later than other types. For example, some types of chemotherapy drugs raise the risk of heart and lung problems later in life, years after chemotherapy was given.

Thinking and memory changes

Chemotherapy can cause you to have trouble thinking clearly and concentrating. This is often called “chemo brain.” These effects can go away after chemotherapy is finished or may last up to a year after treatment is over. Sometimes these effects happen long after treatment is finished. Your healthcare team can suggest ways to help improve concentration and manage changes in memory. They may suggest cognitive exercises that help retrain memory and improve concentration.

Sexual and fertility problems

Chemotherapy can cause you to feel tired and lose interest in sex. It can also damage the reproductive organs and cause fertility problems. It can also lead to treatment-induced menopause in women.

Talk to your doctor before starting treatment if keeping your fertility is important to you. There may be ways to protect your reproductive organs during treatment. This may make it possible for you to get pregnant or get someone else pregnant after treatment.

Second cancers

Some types of chemotherapy drugs increase the risk of developing a second cancer, but this doesn’t happen very often. People who receive both radiation therapy and chemotherapy have the highest risk of developing a second cancer. The benefit of treating cancer usually far outweighs the risk of developing a second cancer. If a second cancer develops, it tends to develop later in life.

Note: Other side effects may occur. For more detailed information on specific drugs, go to sources of drug information.

Expert review and references

Medical disclaimer

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