Brief Answer:
different possible causes

Detailed Answer:
HI, thanks for using healthcare magic

Persistent diarrhea can be due to different possible causes.

The stool sample would have checked for infection, if this was definitely ruled out then you would need to consider other causes such as: (A) food intolerance and lactose intolerance

If it comes and goes, it may mean that there is an intolerance to particular foods. You may want to consider a food diary so that you could note down the foods/drinks that you use to see if any seem to cause this problem

(b)diabetes - long term diabetes can affect how the bowel works and cause diarrhea.

(C)irritable bowel syndrome (IBS)- this is a common cause

(D)thyroid disease- high levels of thyroid hormone can cause this problem

(E)side effect of medication- if you are using any meds, would need to look to see if this is a possible side effect

(F)inflammatory bowel diseases such as crohns or ulcerative colitis can also cause diarrhea

To determine the cause, you may need to : (A) repeat a stool sample to make sure definitely there is no infection

(B)blood tests such as complete blood count, ESR (checks for inflammation in the body) and thyroid blood tests

(C)food diary

(D) if no obvious cause then imaging eg a scope of the intestines, may be needed

I hope this helps, feel free to ask any other questions

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