Is it norman for a woman in her early 40's to have blood clots during her period?

Yes it is very normal. You will probably start to notice a lot of changes in the coming years with your period. The closer you get to menopause, the stranger things get. Have you ever had clots before? How large are they? Are you experiencing a lot of pain? Foul odor? Check with your doctor just to be sure, but I would say your OK!:)