Besides cancer cells, chemotherapy also damages healthy cells that grow and divide quickly (such as the cells lining the mouth and gut and the cells that grow hair); this is why it causes side effects such as mouth sores, nausea and hair loss, and the number of white blood cells may also fall [1, 2]. The most common side effect is tiredness, and most side effects improve or go away after chemotherapy ends [1]. A temperature of 38 °C or higher during treatment can be a sign of a dangerous infection and needs an urgent call to the treatment team [2].
Key points
- The type and severity of side effects depend on the type and dose of the drugs, the type and stage of the cancer and the person's health before treatment; no one can predict exactly how each person will feel [1].
- Exercise and psychological interventions have been more effective than medicines at reducing cancer-related fatigue [3].
- In one study, scalp cooling prevented severe hair loss in about half of women with breast cancer; without it, all had severe hair loss [5].
Why does chemotherapy have side effects?
Chemotherapy works by killing or stopping the growth of fast-dividing cells. Cancer cells are like this, but some healthy cells in the body also divide quickly, such as the cells lining the mouth and gut and the cells that make hair grow. Damage to these cells causes side effects such as mouth sores, nausea and hair loss [1].
Chemotherapy also lowers the number of white blood cells (neutrophils) at certain times in each cycle and raises the risk of infection. This is why regular blood tests are done, and sometimes medicines are given to prevent infection or raise white blood cells [2].
Common side effects and how to manage them
| Side effect | Explanation | What helps? |
|---|---|---|
| Tiredness | The most common side effect of chemotherapy [1] | Planning rest on the day of treatment and the day after, getting help with travel and housework [1]; exercise and psychological interventions [3] |
| Nausea and vomiting | Among the most distressing side effects for patients [4] | Preventive anti-sickness medicines based on how likely the regimen is to cause nausea; the plan can be adjusted in later cycles [4] |
| Low white blood cells and infection | Neutrophils are low at certain times in each cycle [2] | Washing hands often, keeping away from sick people, food safety and regular blood tests [2] |
| Hair loss | Only some chemotherapy drugs cause hair loss [8] | Scalp cooling with some regimens [5]; hair usually grows back 2 to 3 months after treatment ends [8] |
| Mouth sores and eating problems | Damage to the cells lining the mouth and gut [1] | Tell your doctor or nurse, and see a dietitian [1] |
| Peripheral neuropathy (tingling, numbness or pain in the hands and feet) | With some chemotherapy drugs; may persist after treatment [6] | No medicine is recommended for prevention; in severe neuropathy, delaying, lowering the dose or switching drugs is considered, and duloxetine is the only medicine with evidence for painful neuropathy [6] |
| Effect on fertility | Some treatments can reduce fertility [7] | Discuss fertility preservation before treatment starts; freezing sperm, eggs or embryos are the standard methods [7] |
Are the side effects of chemotherapy permanent?
Most side effects improve or go away after chemotherapy ends [1]. Even so, some side effects may last; for example, chemotherapy-induced peripheral neuropathy persists in a number of cancer survivors [6], and some treatments may reduce fertility, which is why fertility preservation should be discussed as early as possible, before treatment starts [7].
When should I see a doctor straight away?
During chemotherapy, contact your treatment team straight away or go to an emergency department if you have any of these signs [2]:
- A temperature of 38 °C or higher, or chills
- Cough, sore throat, earache, headache or a stiff neck
- Diarrhoea
- Burning when passing urine, or bloody or cloudy urine
- Sores or a white coating in the mouth, or a skin rash
- Redness or swelling, especially where a catheter or port enters the skin
Talk to your doctor before taking any medicine for fever (even paracetamol or ibuprofen); these medicines may hide the signs of a serious problem [2].
If you are in pain, do not put up with it: Cancer pain can be treated.
Related questions
Do more severe side effects mean the treatment is working better?
No. Side effects have nothing to do with how well chemotherapy is working against the cancer, and having no side effects does not mean the treatment is not working [1].
Does everyone lose their hair?
No. Only some types of chemotherapy cause hair loss; ask your treatment team whether your medicine does [8].
Do I need a special diet during chemotherapy?
If you have trouble eating, tell your doctor or nurse; seeing a dietitian can also help [1].
References
8 referencesShow all references, 5 with a study cardClose the reference list
Numbers in the text, such as [1], refer to these sources. Sources with a “Study card” button are summarised in the site’s evidence library.
- 1
- 2
- 3Comparison of Pharmaceutical, Psychological, and Exercise Treatments for Cancer-Related Fatigue
- 42023 MASCC and ESMO guideline update for the prevention of chemotherapy- and radiotherapy-induced nausea and vomiting
- 5Effect of a Scalp Cooling Device on Alopecia in Women Undergoing Chemotherapy for Breast Cancer
- 6
- 7
- 8
This page is based on reputable scientific sources and was last updated on 28 October 2026. The content of this website is for educational and informational purposes only and does not replace consultation, diagnosis or treatment by a specialist physician. Consult your treating physician about any treatment decision.
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