Before you make any significant changes to your diet, even if you think your changes will be healthy, you should consult with your physician or a registered dietitian.  Many health conditions and prescription medications must be taken into account when planning a diet plan, so consulting with a professional will keep you safe and healthy. A registered dietitian is an expert who has completed education, training, and supervision in the field of nutrition. Dietitians can help you determine a healthy diet and fitness plan that will account for any health conditions you have and medications or supplements you take. Implementing changes to what you're eating on a daily basis in a gradual fashion will help your body adjust appropriately. Sometimes altering your diet can cause unpleasant symptoms as your body adjusts to the new foods and eliminates the remnants of the old foods. Making gradual changes will also ease any cravings you may feel for what you used to eat, such as sugary treats or salty snacks. Folate is a water-soluble B vitamin; folic acid and food folate are both sources of folate. Folate deficiency can cause your bone marrow to have difficulty making enough platelets.  The recommended daily intake of folate varies, but adults should usually have between 400mcg and 600mcg a day. A full list of recommended daily allowances by age can be found at the National Institutes of Health website here.  Beef liver, leafy and dark green vegetables, legumes, fortified cereals, and nuts are good sources of folate. If you don't consume enough vitamin B12, your bone marrow may have difficulty making enough platelets. Vitamin B12 is also essential to red blood cell formation.  The recommended daily intake of B12 varies, but adults should usually have between 2.4mcg and 2.8mcg daily. A full list of recommended daily allowances by age can be found at the National Institutes of Health website here. B12 is commonly found in animal products, so vegetarians and vegans may need a supplement. Good dietary sources of B12...

TL;DR in Vietnamese:
Nhờ bác sĩ hay chuyên gia dinh dưỡng tư vấn. Thay đổi chế độ ăn từ từ. Ăn thực phẩm chứa folate. Ăn thực phẩm chứa vitamin B12. Ăn men vi sinh. Áp dụng chế độ ăn cân đối với thực phẩm tươi. Loại trừ thực phẩm đã qua chế biến và thực phẩm chứa nhiều đường.