slight fever; low-grade fever
Used for a mild fever, often not very high but enough to make someone feel unwell or require caution.
I have had a slight fever since morning, so I will rest at home today.
If the low-grade fever continues, you should go to the hospital.
I've had a slight fever since yesterday.
I've had a low-grade fever for a whole week now.
I have a slight fever, so I'll take the day off.
After taking medicine, my slight fever went down.