If you wait too long to start the med, it won't reach full potential before it's time to test, if your doctor is having you test in 6 weeks, which is typical when just starting out, since it takes 4-6 weeks for the med to reach full potential in your blood. You might try splitting
the pills for a few days to make sure you tolerate it before you take the full 50 mcg if that would make you feel more comfortable.
Don't go by other people's horror stories. Those aren't that common.