Rob
Ansys Employee

Generally no. It can be worth running one case laminar & again turbulent to see if there's a significant difference. Reason being if you're borderline transitional due to flow conditions (not Re - that's a guide) it can show up in the turbulent case. 

Note, depending on conditions transition flow in a pipe can occur at Re 800-1000   The undergrad experiment when I was at Uni gave very odd results every 20mins: that coincided with a bus parking outside....