Leukemia and lymphoma are cancers that affect your bone marrow. That’s where all your blood cells come from. These conditions disrupt your body’s process for making red blood cells. So there’s not enough of them to carry oxygen to other parts of your body.

Gastrointestinal cancers, like stomach or colon cancer, can cause anaemia. Bleeding often happens with these conditions. When you bleed a lot, you lose red blood cells faster than your body is able to make them.

Your kidneys make a hormone that triggers your bone marrow to make red blood cells. If you have kidney cancer, or if cancer treatment affects your kidneys, they might not work the right way. So your bone marrow doesn’t get the signal to make red blood cells.

Nearly every cancer can metastasize, or spread from where it started. For instance, breast and prostate cancer cells may travel to your bone marrow. Then, like leukemia and lymphoma, they could affect the amount of blood cells your bone marrow makes.