Eat a diet low in iron, vitamin B12, and folate
Skip meals regularly
Follow a very restrictive diet without medical guidance
Lose blood through heavy menstrual bleeding
Donate blood frequently
Have untreated stomach or intestinal bleeding
Have chronic diseases that affect blood production
Have conditions that reduce nutrient absorption
Take medications that can cause bleeding or affect red blood cell production
Drink excessive alcohol
Have inherited blood disorders
Be pregnant without adequate iron and vitamin intake