How long should I go without sleep before seeking medical help?

So I haven't slept for the past two nights. This is fairly unusual for me, though not unheard of. I also am feeling very anxious, which might be both a cause and result of this lack of sleep. I know that insomnia is defined as a trouble sleeping over a longer time, like a month, but my question is, how long should I go without sleep before I decide to seek some kind of medical help? If I go to the doctor or somebody after not sleeping for 4 days, will they laugh and tell me to come back in a month?