Can you please post your code; and just in case, don't forget to use code tags for that 
Which board are you using?
What is the receiving end? A PC? Running which OS? Which application?
Two points to be aware off
- There is a serial software buffer with 64 bytes; if you print faster than the buffer can be emptied, your code will slow down.
- Hiccups can be caused at the receiving end.