Doctors can you tell me how often should asthmatics have blood tests?

Not often: Lab work is not routinely needed for asthma, however your doc may be checking other things. Sometimes we check levels of an antibody called ige to see if patients qualify for a particular medication. Also, some medications that are occassionally used for asthma may require monitoring of drug levels or liver enzymes (3-4x year). However most asthma patients with mild/mod disease need few labs.