Written by Mash Media editorialClinically reviewed by Dr. Harshvardhan Atreya on 1 October 2026Published 1 October 2026
Why a fever matters more during chemo
Chemotherapy lowers the white blood cells that fight infection, usually reaching the lowest point 7–14 days after a dose. During that window an infection can spread quickly and quietly, because the usual warning signs are muted.
The rule
A single temperature reading of 100.4 °F (38 °C) or higher, or 100.0 °F sustained for an hour, during chemotherapy means: call the oncology team now, or go to the emergency department. Do not wait to "see if it settles", and do not take paracetamol first to bring it down — that hides the signal.
What happens next
The team will check your blood counts and usually start antibiotics within the hour if your counts are low. Most people go home well within a few days. The danger is delay, not the fever itself.