How long is nicotine detectable through a blood test?

Three days: Nicotine can be detected in your system from anywhere between three days to several months. It depends upon how much you smoke, how long you've smoked for, and what type of test is administered.

Cotinine: “When someone stops using tobacco and nicotine products, it can take more than two weeks for the blood level of cotinine to drop to the level that a non-tobacco user would have and several weeks more for the urine level to decrease to a very low concentration.” REF: http://labtestsonline.org/understanding/analytes/nicotine/tab/test/