I have had hypothyroidism since I was born and I am now 17 years old and am taking synthroid at 200 mcg. I am supposed to take it everyday but it is hard to remember so I miss at least 4 days at a time. I rarely feel hungry and when I do eat, I get full fast but I also drink alot of soda when I eat so that may be the reason but I eat a whole lot of junk food but I am only 130 pounds at 5'6. Sometimes when I lay down for awhile and get up, I get dizzy and my vision fades out for a while and sometimes I get a headache after I nap. I am also very lethargic and must take energy pills to get through work. I get about at least 8 hours of sleep at night so that can't be it, and sometimes I don't handle heat too well and feel a little weak. Does anyone know if that is cause by hypothryoidism and if I should see a doctor right away? I have not checked my thyroid for about a year and last time it was low.