I learned that eating enough green vegetables, examples spinach, pumpkin leaves and a lot more others can help build blood in the body. Also eating fishes, crustaceans, crayfish are also good for gaining blood in the body. Well, I am not a nutritionist you may discuss with your nutritionist or doctor too.
Along with healthy eating it is recommended that you start iron and folic acid supplements as food alone can not suffice to meet extra demand of blood for two individuals. It is wise to take your iron supplement with a piece of meat for maximum absorption. Coloured vegetables like beetroot and green leaves add a lot of iron to the body and liver is also a good source of iron.
You need to eat iron rich foods to increase hemoglobin. Green leafy vegetables are rich with iron. You can also take iron supplements. Alternatively you can eat food cooked on raw iron utensils.
Iron from heme sources are better absorbed by the body. Some of the best heme sources are chicken liver, mussels, clams, oysters, and beef. The non-heme iron are found in plants and in animal meats. Some of the best sources are pumpkin and squash seeds, nuts, white beans, lentils, and moringa. My body rejects iron supplements so I had to ensure that I'm getting enough iron in my diet before, during, and after pregnancy.
I think it is not during pregnancy but you can increase your hemoglobin if you - 1. Increase intake of vitamin C 2 eat beetroots, folic acid, fruits like apples, guava 3. Eat eggs, meats, dairy products, dry fruits and leafy vegetables.