What could be the cause of my mother in law's low creatinine level?

My mother in law, 72, has had chf for at least 7 yrs. She is diabetic, has pulmonary fibrosis, recurrent cellulitis, stents in heart and legs, hypothyroidism, high colesteral, sleep apnea, recurrent UTI, and uses a nebulizer. She takes 14 prescriptions every day including very strong fluid pills every day. She has been on hospice for 3yrs. Requires 95% care. She can only walk about 10ft with assistance, 98% inactive. She uses oxygen 24/7. For the last 2 wks she has been vomiting, had loose bowels, is dizzy, chest pains, and extreme fatigue. BP runs 100/48. Blood wrk shows potassium is ok. She is not dehydrated and her white count is ok. But, her creatinine level was critically low. What could be the cause of all this?