Can you explain if your hemoglobin is low what cause's this and how it can be put right?

Low hemoglobin. Low hemoglobin is called anemia. There are many causes of anemia- from congenital disorders , blood loss, nutrient deficiency, destruction, autoimmune etc. To correct it, you need to know the cause of it. My advise for you is to see your pcp who can help you with running some basic work-up. If needed, your pcp can refer you to see a hematologist. Good luck.