My Mother Has Been Dealing With A Soft Stool For

My Mother has been dealing with a soft stool for weeks now. I'm working with her primary physician to treat the matter with diet. My Mother was constipated after she came out of the hospital (May 9, 2018) and that was corrected with diet. Within the last few weeks, she has had a loose stool off and on (over the last week of so, its been on). Is it okay to give my mother oatmeal with Stevia in it?