Weak positive IgM for Mycoplasma pneumoniae is not normal and suggests a Mycoplasma pneumoniae infection. Mycoplasma pneumoniae is a pathogen, the smallest microorganism that can live independently, and is mainly transmitted through the respiratory tract. After Mycoplasma pneumoniae infection, the body can produce IgM, about one week after infection, at this time the antibody concentration is low, the test results are mostly weakly positive. As the disease progresses, the concentration of IgM in the blood becomes higher and higher, reaching a maximum value at 4 to 6 weeks, when it can be strongly positive. Over time, the concentration of IgM in the blood gradually decreases, at which time the IgM test is again weakly positive. Weakly positive IgM of Mycoplasma pneumoniae needs to go to a regular hospital and follow the doctor’s instructions.