I have extremely low iron, to the point that I collapse at any given time. I also take Ferrograd C. Like cookiemonster said, don't drink tea or coffee one hour either side of taking it. Also eat plenty of red meat, and put salt on your food. You can get Ferrograd C over the counter at the chemist.
It might be best to also get your iron levels checked with your gp. My gp has said that if the Ferrograd doesn't boost my levels, than I'll need an iron fusion.