Why does febrile neutropenia cause unexplained fever?

Neutrophils are white blood cells that help contain bacteria and fungi. When their number is low, an infection may develop quickly and may not produce the usual signs, such as pus, redness, or a strong local reaction. Fever can therefore be the first or only noticeable clue. The cause may be difficult to identify at first because the weakened immune response can make symptoms less obvious.

Febrile neutropenia can happen during cancer treatment or with other medical causes of low neutrophils. Fever may also have non-infectious causes, but it should be treated as urgent in someone known to have neutropenia until a healthcare team has assessed it.

Follow the fever plan given by your oncology team. Check your temperature with the recommended method, write down the reading and time, and contact the team immediately using its urgent number. Tell them about chills, cough, breathlessness, sore throat, diarrhoea, pain when passing urine, a new rash, or confusion. Do not delay by taking fever-lowering medicine unless the team has told you to do so, because it can hide a change that clinicians need to assess.

Any fever during known or suspected neutropenia needs prompt medical advice, even when you feel reasonably well or cannot find an obvious source. Seek emergency help for difficulty breathing, confusion, fainting, severe weakness, shaking chills, chest pain, or rapidly worsening illness. Bring your treatment details and tell staff that your neutrophil count may be low.

Ask what temperature threshold and phone number apply to your treatment plan, how to check temperature, which medicines to avoid, and where to go outside clinic hours. Ask how long neutropenia may last, which infection symptoms to watch for, and when blood tests should be repeated.