I don't have middle ear infection but when I stand up I feel dizzy, light headed & get hot flushes. Could it be low blood sugar or something else?

Yes. It could be due to low blood pressure. See a doctor if you can to get your blood pressure checked out. Eat and drink regularly, as dehydration can also trigger this.
hypotension. If you have been sitting or lying , your blood tends to stagnate in your lower extremities and if you get up to quickly the blood can't get up to you brain for an instant and you can feel dizzy and light headed.