In most heavy smokers, cotinine levels fall below the detectable range after two weeks of abstinence, according to Mayo Clinic. This means that the laboratory test will show a value of less than 2 nanograms of cotinine per milliliter of blood.
The rate of metabolism of nicotine and cotinine depends on the genetic makeup of the individual. Genetic variations play an important role in the way that drugs are metabolized and the amount of metabolic enzymes that a person’s body produces. This can have a significant impact on the rate of cotinine metabolism.
The average half-life of nicotine is two hours, while the half-life of cotinine is 15 hours. The range of cotinine in the blood of active nicotine users is between 200 and 800 nanograms per milliliter. While these levels are elevated in both tobacco users and individuals undergoing nicotine replacement therapy, laboratories can determine what type of nicotine a person is using by testing for the presence of anabasine in the urine. This alkaloid is present in the urine of tobacco smokers and is absent if one is using a tobacco-free alternative.
Elevated levels of cotinine have been found in individuals exposed to second-hand smoking. Levels as high as 8 nanograms per milliliter have been reported, and with 2 nanograms per milliliter being the cutoff, this will result in a positive cotinine test for someone exposed to tobacco smoke, according to Mayo Clinic.