Key points
- A temperature of 38 °C or higher during chemotherapy is an emergency, even if you feel well. Contact your treatment team straight away, even in the middle of the night; do not wait until morning [1].
- Before taking any medicine for a fever, even paracetamol (acetaminophen) or ibuprofen, talk to your doctor or nurse [2, 3].
- White blood cells are usually at their lowest 7 to 12 days after chemotherapy; during these days an infection can become serious very quickly [4, 5].
- In hospital, antibiotics should be started within the first hour. Say straight away: "I have cancer and I am having chemotherapy" [4, 7].
- Other warning signs: shivering, confusion, shortness of breath, chest pain, bleeding that will not stop, vomiting that stops you drinking, a swollen and painful leg, and yellow skin or eyes [3, 4, 9, 10].
- Take a cold during chemotherapy seriously: with a fever it is an emergency; without a fever, still tell your treatment team [1, 2].
Fever during chemo: is it normal?
No. Never treat a temperature of 38 °C or higher during chemotherapy as normal. The US Centers for Disease Control and Prevention calls it an emergency and advises calling your doctor straight away, even in the middle of the night; do not wait until morning [1].
This is because chemotherapy lowers the number of white blood cells. These cells fight germs. When there are few of them, an infection can become serious very quickly and lead to sepsis, the body's extreme response to an infection, which is life-threatening [4].
White blood cells are usually at their lowest 7 to 12 days after each dose. The timing differs with different drugs, and your treatment team will tell you when to expect it [5]. But a fever on any day during chemotherapy needs to be reported [1].
What is a high temperature for a cancer patient?
For someone having chemotherapy, 38 °C or higher counts as a fever that must be reported straight away [1, 2]. Your own doctor may give you a different number; if so, follow that [3].
- Keep a digital thermometer at home [3].
- Take your temperature at least once a day, or as often as your treatment team tells you [3]. Also take it whenever you shiver or feel unwell [1].
- Write down the reading and the time so that you can tell the doctor.
There can be danger even without a fever: if you suddenly feel unwell during treatment, for example you are shivering, feel very cold, are confused or short of breath, you need to be checked straight away, even if the thermometer does not show a fever [4, 6].
When should I contact a doctor?
Contact your treatment team straight away or go to the emergency department if:
- you have a temperature of 38 °C or higher, even if you feel well [1];
- you have shivering or sweats, or feel very cold [2, 4];
- you are confused or very drowsy, your heart is racing, your skin is clammy or sweaty, or you are in extreme pain; these can be signs of sepsis [3, 4];
- you are short of breath or have chest pain, especially pain that gets worse when you breathe in deeply or cough, or you cough up blood [9, 10];
- a leg or arm is swollen and painful, or warm or red [9];
- you have bleeding that will not stop, red or pink urine, black or bloody stools, or bleeding from your gums or nose [3];
- you have been vomiting for more than a day, or you bring up everything you drink [3];
- diarrhoea has lasted more than 24 hours or comes with pain and cramps [3]. If you take capecitabine tablets and your number of bowel movements a day has gone up by 4 or more compared with what is usual for you, or you have diarrhoea at night, stop the tablets and call straight away [10];
- your skin or the whites of your eyes have turned yellow [10];
- your mouth is very painful [3];
- the area around your port or catheter is red or swollen [2];
- you have a severe headache or changes in your vision [3].
Night-time or a weekend is no reason to wait [1, 3]. If you suddenly feel very unwell, for example with severe shortness of breath, chest pain or fainting, call your local emergency number.
Why is a fever with low white blood cells an emergency?
A fever together with a very low level of one type of white blood cell (neutrophils) is called "febrile neutropenia" [8]. In this situation the body cannot stop germs from spreading, and an infection can turn into sepsis very quickly [4].
That is why guidelines say antibiotics should be started within the first hour after arriving at hospital [7]. Doctors should check anyone having cancer treatment who becomes unwell for this infection, even if they do not have a fever [6].
After blood tests and an examination, the doctor assesses the risk. Some people at low risk can be treated at home with antibiotic tablets after being observed for at least 4 hours; others are admitted to hospital [7]. Read more: Low blood counts and preventing infection.
When to go to the ER during chemo, and what to say there
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Take these with you
The names of your chemotherapy drugs and the date of your last dose, the name of your doctor and treatment centre, your latest blood test results, a list of the medicines you take, and your temperature reading and the time it was taken. Say whether you have taken any medicine for the fever.
Colds during chemotherapy
During chemotherapy, a sore throat, a cough or a blocked nose can be the start of an infection [2, 4].
- If you also have a temperature of 38 °C or higher, it is an emergency; contact your team straight away [1].
- If you do not have a fever, still tell your treatment team [2] and check your temperature regularly [3].
- Before taking any medicine for a fever, even paracetamol (acetaminophen), talk to your doctor or nurse [2, 3]. Do not start cold remedies without asking your doctor or pharmacist either [3].
To prevent infections: wash your hands often, stay away from people who are ill and from crowds, and wear a mask outside your home when respiratory viruses are going around [2, 4]. Have the flu vaccine every year and ask the people you live with to keep their vaccinations up to date [4, 11]. For the people around you, see Is chemotherapy dangerous for the people around me?
Which symptoms can wait for a phone call? (A card to print)
| What should I do? | Symptoms |
|---|---|
| Go to the emergency department or call straight away | Temperature of 38 °C or higher; shivering; confusion; shortness of breath or chest pain; bleeding that will not stop; vomiting that stops you drinking; a swollen, painful leg; yellow skin or eyes [1, 3, 4, 9, 10] |
| Contact your treatment team today | Sore throat, cough or blocked nose without a fever; burning when passing urine; diarrhoea for more than 24 hours; vomiting for more than a day; a very sore mouth; redness around a port; new bruises without a knock; new tingling or numbness in the hands or feet [2, 3] |
| Mention at your next appointment, if it has not got worse | Tiredness that does not stop your daily activities; nausea that is controlled by anti-sickness medicine; hair loss; changes in how food tastes [3] |
Print this card and keep it by the phone or on the fridge. Write your treatment team's night-time number and the nearest emergency department on it.
Frequently asked questions
I have a fever and chills after chemo; what should I do?
How can I tell whether a fever is from an infection or from the drug itself?
What are the signs that chemo is doing serious harm?
Most side effects of chemotherapy are unpleasant but can be controlled with medicines and care [3]. The signs that something serious is happening and that you need help straight away are in the section "When should I contact a doctor?": fever, shivering, confusion, shortness of breath, chest pain, bleeding, a swollen leg, yellowing, vomiting that stops you drinking, and diarrhoea that lasts more than a day [3, 4, 9, 10].
What if it is night-time or a weekend?
The emergency department said I can be treated at home with antibiotic tablets; is that right?
Yes, it can be. If, after an examination and tests, the doctor judges the risk to be low, some people go home with antibiotic tablets after being observed for at least 4 hours. If the fever has not settled within 2 to 3 days, you need to be checked again and may be admitted [7].
I have a cold but no fever; should I tell my doctor?
Related pages
- Your first chemotherapy session: what to expect
- Low blood counts and preventing infection
- What are the side effects of chemotherapy?
- Nausea and vomiting during cancer treatment
- Constipation and diarrhoea during cancer treatment
- Mouth sores (mucositis)
- Caring for a port or PICC line
- A guide for family members and caregivers of people with cancer
Febrile neutropenia and warning signs (for physicians)
Show detailsHide
Definition (IDSA 2011). Fever: a single oral temperature of ≥38.3 °C, or ≥38.0 °C sustained over 1 hour. Neutropenia: ANC below 500 cells/mm3, or an ANC expected to fall below 500 during the next 48 hours; profound neutropenia: ANC below 100 [8]. NICE CG151 defines neutropenic sepsis as a neutrophil count of 0.5 × 109/L or lower with a temperature higher than 38 °C or other signs or symptoms consistent with clinically significant sepsis; it should be suspected in anyone having anticancer treatment who becomes unwell, with immediate referral and empirical antibiotics started immediately [6].
Timing and setting (ASCO/IDSA 2018). First dose of empirical antibiotics within 1 hour of triage and monitoring for ≥4 hours before discharge. Outpatient candidates selected by clinical judgement or a validated tool such as the MASCC index. Outpatient regimen: an oral fluoroquinolone plus amoxicillin/clavulanate (or clindamycin if penicillin-allergic), unless fluoroquinolone prophylaxis was used before the fever. No defervescence after 2 to 3 days: re-evaluate and consider admission [7]. Details in Febrile neutropenia: assessment, empirical antibiotics and outpatient treatment and MASCC score for febrile neutropenia.
Patient education. NICE recommends written and oral information on neutropenic sepsis, how to contact 24-hour specialist oncology advice and when to seek emergency care, before and throughout treatment [6]. Patient materials use 38 °C as the threshold for calling [1, 2], and the neutrophil nadir is often on days 7 to 12 [5]. Capecitabine label: stop the drug and call at once for an increase of 4 or more bowel movements a day over baseline or nocturnal diarrhoea, and stop and seek emergency care for chest pain, dizziness or shortness of breath; a fever of 100.5 °F or higher and jaundice should also be reported immediately [10]. Other emergencies (tumour lysis syndrome, hypercalcaemia, spinal cord compression, superior vena cava syndrome): Oncological emergencies.
References
11 referencesShow all references, 3 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.
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- 11Vaccination of Adults With Cancer: ASCO Guideline
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.
Printed from the website; the full and up-to-date version: https://drdabiri.com/en/guides/chemo-warning-signs/