Anemia Share this with others:Anemia, which is defined as a decreased number of red blood cells or hemoglobin, can lower the amount of oxygen reaching the brain. Any lowering of oxygen reaching the brain can cause a swelling of the arteries of the area, causing headaches. Get Free Email Updates!Get News to Know, webinar annoucements & information on upcoming programs. NHF will never give away, trade or sell your email address. You can unsubscribe at any time.