When is a fever an emergency?

During chemotherapy, always. A temperature of 38 degrees Celsius or 100.4 Fahrenheit needs a phone call straight away, day or night, even if you feel otherwise fine.

This is the one thing on these cards we would rather you over-react to. Treatment can lower the cells that fight infection, and an infection can move fast. Do not wait until morning.

Written by two physicians. Checked against patient information from the US National Cancer Institute and Cancer Research UK.