Treatment and the treatment process

Antibiotics

Leukemia and its treatment weaken the body’s defences against infection. Antibiotics are an integral part of care: they prevent and treat bacterial infections.

Last updated: 14 October 2026~2 min read

A cluster of faintly red-glowing bacteria on a dark navy background held back by a teal shield. — **Figure 1.**Antibiotics protect the body from bacteria during neutropenia.

01Short answer

After chemotherapy, neutrophils — the main cells that fight bacteria — fall very low (neutropenia). At this time even ordinary bacteria can cause serious infection and sepsis, and sometimes the only sign is a fever. So with fever during neutropenia (febrile neutropenia), a broad-spectrum antibiotic is started into a vein straight away, usually after blood cultures are taken. Depending on results and progress, the antibiotic may be changed or stopped. In some situations — such as acute leukemia when long and deep neutropenia is expected — a preventive antibiotic (for example a fluoroquinolone) is given as tablets. Co-trimoxazole is often used to prevent pneumocystis pneumonia. It is important to take antibiotics as prescribed and not to stop the course early.

02Simple explanation

Why? When neutrophils are low, bacteria easily cause infection.

Fever is a signal. Sometimes it is the only sign of infection.

Start fast. The sooner an antibiotic starts, the safer.

Prevention. Sometimes a protective antibiotic is given even without infection.

03Scientific explanation

Febrile neutropenia: neutrophils <0.5×10⁹/L (or expected to fall) and a temperature of ≥38.0–38.3 °C. According to ESMO, IDSA and NICE, a broad-spectrum beta-lactam (such as piperacillin–tazobactam, cefepime or meropenem) should start within an hour; risk is assessed with the MASCC score.

Prevention: in prolonged neutropenia, fluoroquinolone prophylaxis reduces infections and, in some studies, deaths, but raises the risk of resistance — centres decide based on local data. Co-trimoxazole against pneumocystis is standard in ALL and some other regimens.

Resistance and stewardship: careful antibiotic use (antimicrobial stewardship) — narrowing the spectrum according to cultures and avoiding unnecessary length — helps prevent multidrug-resistant bacteria and C. difficile diarrhoea.

04What happens in the body?

What to do with a fever

Take your temperature; if it is 38 °C or higher, call the number your team gave you straight away. In hospital, blood tests and cultures are taken and antibiotics start. Do not take fever medicine without talking to your doctor.

A glowing clock face without numbers with a gold-highlighted short arc and a thermometer shape on a dark background. — **Figure 2.**With fever during neutropenia, antibiotics should start within about an hour.

Cultures

The laboratory tries to find bacteria in the blood or other samples and tests which antibiotic works against them. Results usually take 1–3 days, so a broad-spectrum antibiotic is given first.

Laboratory dishes with softly glowing colonies under a microscope lamp. — **Figure 3.**Cultures find the bacteria and help choose the antibiotic.

Preventive antibiotics

During some treatment periods, an antibiotic tablet may be prescribed to prevent infection. It does not replace urgent help when you have a fever.

05Fever during neutropenia: what happens?

A simplified outline.

1FeverTake your temperature.

2CallYour team, straight away.

3TestsBlood cultures.

4AntibioticWithin an hour.

Early treatmentPreventing sepsis.

CultureA precise choice.

PreventionIn some periods.

06How antibiotics are used in leukemia

Purpose	Example	Note
Febrile neutropenia	Piperacillin–tazobactam, cefepime, meropenem	Into a vein, urgently
Prevention	Fluoroquinolone (levofloxacin)	In prolonged neutropenia
Pneumocystis prevention	Co-trimoxazole	ALL and other regimens
Catheter infection	Vancomycin and others	Guided by culture
Gut infection	C. difficile treatment	If diarrhoea occurs
Outpatient treatment	Antibiotics by mouth	Low risk, doctor’s decision

* Only your doctor chooses the antibiotic and how long to take it.

07Key terms

Neutrophil: A white blood cell that fights bacteria.
Neutropenia: A shortage of neutrophils.
Febrile neutropenia: Fever during neutropenia — an emergency.
Blood culture: A test looking for bacteria in the blood.
Broad-spectrum antibiotic: An antibiotic that acts on many bacteria.
Sepsis: A life-threatening reaction of the body to infection.

08Key points

Infection risk is high during neutropenia.
Fever is an emergency.
Antibiotics should start within an hour.
Cultures refine the choice.
Preventive antibiotics may be used.
Do not stop the course early.

09Frequently asked questions

I have no fever but feel unwell — should I call?

Yes. Shivering, weakness or confusion can also be signs of infection.

Can I take paracetamol?

During neutropenia, do not take it before you have measured your temperature and called your team.

Can antibiotics cause diarrhoea?

Yes; tell your team if you have frequent watery stools.

Can I take antibiotics at home?

Sometimes, if the risk is low, and only by the doctor’s decision.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

I have no fever but feel unwell — should I call?
Can I take paracetamol?
Can antibiotics cause diarrhoea?
Can I take antibiotics at home?

My questions

12Sources

National Cancer Institute (NCI). Chemotherapy to Treat Cancer
Cancer Research UK. Chemotherapy
NHS. Chemotherapy
National Cancer Institute (NCI). Infection and Neutropenia during Cancer Treatment
American Cancer Society. Infections in People with Cancer
NHS. Neutropenic sepsis
MedlinePlus. Uric acid – blood
MedlinePlus. Febuxostat
Canadian Cancer Society. Kidney problems
MedlinePlus. Acute kidney failure

Medical disclaimerThis information is for educational purposes only and does not replace medical advice.

Last updated: 14 October 2026← Back to the list

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