Hi, dear I have gone through your question. I can understand your concern. In cancer patients also hemoglobin should be kept above 12. There is no harm in that. In spite it is necessary to maintain hemoglobin above 12 for healthy living. So it has no relation with thicker blood and all that. Myeloproliferative disease can cause thicker blood but for that aspirin and hydroxyurea should be given. But I m not agree with that theory of low hemoglobin. Hope I have answered your question, if you have doubt then I will be happy to answer. Thanks for using health care magic. Wish you a very good health.