I Am 67 Years Old , Quite Healthy., Take Pravaststi,

I am 67 years old , quite healthy., take pravaststi, los art in,amlodopine and csrvefilol daily for 5 years. Last year had a colonoscopy and it revealed nothing. Not even a polyp.also had an endoscopy revealing a couple small spots of ulceration in my stomach and evidence of s little gerd. For 6 months I took one omezaprol in the morning and 1famatodine at night.

No evidence of any problems an discontinued per gastroenterologist this therapy,

For years my internist recommended COq 10 daily. I finally figured it would be a good idea and I started taking on ubíquenol 100 mg with breakfast daily. For three days I suddenly have black tarry loose stools I have had no changes at all on my diet. Could this be from the ubiquenol?
Please advise.