<s>[INST] How does low hemoglobin kill a person and is it a painful death? We brought my father in law home on a vent 2 weeks ago to pass, had bypass surgery in January and never got off the vent. Does not want anything done that requires a trip to the hospital. His hemoglobin is at 6 (this has been an issue the last 6 months with many units of blood given), our family understands that this could kill him, we don't want it to be painful. What happens when hemoglobin keeps going lower? [/INST] Hi,Thanks for asking.Based on your query, my opinion is as follows.1. Low hemoglobin leads to deficient oxygenation of tissues, which can cause cellular hypoxia leading to cell death.2. Due to low hemoglobin, the heart performs more activity for more oxygen to reach tissues, this overtime will lead to  cardiac failure.3. Tissue damage can produce free radicals, which cause further tissue injury.4. Cardiac failure, peripheral organs damage and risk of infection are the usual cause of death in severe anemia or low hemoglobin.Hope it helps.Any further queries, happy to help again. </s>