[9] Nonetheless, treatment with cotinine in humans was reported to have no significant physiologic, subjective, or performance effects in one study,[10] though others suggest that this may not be the case.

Cotinine has an in vivo half-life of approximately 20 hours, and is typically detectable for several days (up to one week) after the use of tobacco.

Values of 10 ng/mL to 100 ng/mL are associated with light smoking or moderate passive exposure, and levels above 300 ng/mL are seen in heavy smokers — more than 20 cigarettes a day.

In urine, values between 11 ng/mL and 30 ng/mL may be associated with light smoking or passive exposure, and levels in active smokers typically reach 500 ng/mL or more.

In saliva, values between 1 ng/mL and 30 ng/mL may be associated with light smoking or passive exposure, and levels in active smokers typically reach 100 ng/mL or more.

[21] Cotinine levels can be used in research to explore the question of the amount of nicotine delivered to the user of e-cigarettes, where laboratory smoking machines have many problems replicating real-life conditions.