What Is The Indication Of Chills And Joint Pain In 93 Year Old?

My 93 year old mother has been suffering from chills in the evening (no fever). Temp in the house is at 70. She complains of fatigue. Last blood work showed Creatinine level at 0.90, low EGFR Non Afr American, low WBC and low Neutrophils, Absolute. Was seen by her primary beginning of the week and he did not seem to be concerned. Of course, at the time, I was not aware of the additional symptoms of chills in the evening and joint pain. Would like to go back to the primary with some idea of what could be going on and what else I should be asking my mother.