The control line isn't for clarity of creatine. It is the line to help determine that the test strip is working properly. If you are wanting to take any and all precautions, I would suggest to take the tums and aspirin as described in the sticky. It would be better to cover your a## to do the complete thing in case they send it to the lab. I've been on probation for a while and for the first few times I had to do a UA my test were sent to a lab. Once they thought I was legent it was only dip stick test. Courts tend to EXPECT people to try to cheat so they want to cover their a##es as well.