My uncle is getting fever around 99F every evening. Blood work is okay. He has lost 25 lbs in last 4 months. Please guide?

99 not a fever BUT! 99 IS NOT A FEVER BUT 25# WEIGHT LOSS IS IMPORTANT. He needs to get a full evaluation to clarify the weight loss. Ask him to see his physiciasn and get a full workup. He may need to be seen in consultation. We do not know his age but consider gastrointestinal issues, metabolic issues or even cancer.
Weight loss. That temperature in the evening isn't abnormal, but the weight loss requires a physician's evaluation.