Generally, employers and other testing agencies use a urinalysis test to determine the levels of nicotine, if any, in a person.
How Long Does Nicotine Stay in the Body For?
If you're only an occasional smoker, and when you light up it's just a cigarette or two - the typical social smoker - then the nicotine will generally be clear of your system in three to four days.
For people who smoke steadily, or who have a long history of smoking, it's going to take longer to clear the nicotine from your system. One week to two weeks is a good ballpark figure, but for those with a long history of heavy smoking, you may be looking at twenty days or longer.
How Is It Possible to Detect Nicotine in the Body?
These results are based on testing by urinalysis. Blood testing can detect much smaller amounts, so the time frames lengthen quite a bit. After nicotine enters your blood system, your body converts, (or metabolizes) it into a substance called cotinine. This is actually the substance the blood test measures.
Your body does not clear blood through your system via the liver as fast as urine passes through your system. That's why blood tests can detect substances for longer periods of time than can urine tests.
A third test, a hair test, can analyze substances retained in a person's hair. This test is expensive and is rarely administered, but can detect substances months or even years after a person has stopped using.
How soon a person has to stop using nicotine before a drug test will vary, but for the average person undergoing a urinalysis, twenty days is a good estimate, unless you're a heavy smoker with a long history of smoking. Blood and hair tests take longer, of course, so it might be a good idea to find out what type of testing will be done so you can give yourself the best odds of passing.