Hi, Thanks for query. You did not mention which organ s tuberculosis you are suffering from . Also you did not write whether you are having primary or secondary tuberculosis. I do not agree at all with the anti tuberculosis drug regime you are taking. Giving only two drugs for a period of nine months does not make any sense at all. You should take at least four drugs ( isoniazid, rifampicin, pyrazinamide, ethambutol) for two months followed by isoniazid,rifampicin for four months. If you have an extrapulmonary T.B then treatment duration may be prolonged depending on the response. Probably your doctor increased dose of rifampicin from 450mg to 600 mg. Dose of isoniazid also should be increased from 300mg to 600 mg. Regarding weight gain, you need to worry. Tuberculosis causes weight loss. Resolution of tuberculosis will lead to weight gain due to resolution of disease as well as increased apetite. But you need to immediately consult a pulmonologist regarding how long these medications you need to take. Hope, I answered your queries.