I am currently doing my bodyweight routine as I type this. I would encourage everyone, even those who don't have the disease, to be more active. I have been doing this for about 4 months and I feel great. You could start with the most basic things like pull ups, push ups or signing up for a sport and see how it goes for you, because everyone's body is different. I am not sure if thalassemia can hinder muscle growth, but I have definitely gained strength over the course of the past few months and it's become a hobby of mine. I am currently eating at a surplus to gain muscle mass (I eat very clean for most of the time) and I have big goals for this year. I only currently do bodyweight fitness, but I also plan on either getting a gym membership or picking up something like swimming or volleyball when I turn 18. Until then, I am sure I will have gained a lot of strength and a good amount of muscle mass. The only issue I find is that when it's almost time for a blood transfusion and my hemoglobin gets low, it's a little bit harder to complete my routine and it sometimes takes a little bit more time for my body to fully recover, but once I go for a blood transfusion, I feel like I can lift a mountain. I'd definitely say you should give what you're interested in a try and see how it works for you. Keep us updated and don't be afraid to begin a new adventure in your life!