It is not possible to generalize how long it takes for mycoplasma to turn negative after taking Doxycycline. Usually mycoplasma nucleic acid test can turn negative after about 2 weeks of taking it. Mycoplasma can infect all parts of the body, most of them can infect the genitourinary system, lungs, face, etc. Clinical symptoms related to pneumonia caused by Mycoplasma pneumoniae are more common. Doxycycline belongs to the tetracycline class of antibiotics, which is more effective in treating mycoplasma infections. Most mycoplasma nucleic acid tests are usually negative after about 2 weeks of doxycycline administration. A small number of mycoplasma may be resistant to doxycycline, and the treatment is not effective and does not improve after 2 weeks. Therefore, after 2 weeks of regular doxycycline treatment, if the treatment is not effective, you should choose the appropriate sensitive antibiotics according to the results of the drug sensitivity test. During mycoplasma infection, it is necessary to avoid straining and pay attention to a healthy diet.