Whats the normal hemoglobin level of 40 years old woman? How to improve it?

Varies a little. Your lab might use different "normal", but in general: 12.1 to 15.1 gm/dl = hemoglobin for adult females. If you have chronic diseases (kidney probs, diabetes, etc.), then you should discuss w/your dr, otherwise, iron-rich foods like dark greens (spinach) and red meat (in moderation) are two obvious answers. Multivitamin w/iron (or prenatal vit) can also help. If still low after 3-4 wks, see ur dr.