1. How do you know it was Giardia? Any proper testing by proper lab that fond it? Yes a few cases of Giardia can be quite drug resistant to for example Metrandinazole, for Tinidazole (if right dose) cure rate is according to several sources very high (but yes not fool proof)...
2. How do you know you are cured? Have you been better for many months? or just weeks?
Wonderful if people getting well, but problem is if people think they get well from this or that and think they had this and that....Cearly most sick people have something, question is what...this is where proper diagnose comes in...
Possibly you had such proper diagnose, but we would be happy to know...