Some are in the form of pills and some are drops for children. Most forms of oral iron replacement therapy are absorbed well by the small intestine; however, there are certain preparations of iron supplements that are designed for longer release in the small intestine than other preparations. Oral iron supplements are best taken up by the body on an empty stomach because food can decrease the amount of iron absorbed from the small intestine. The dosing of oral iron replacement therapy is as much as 100–200 mg per day in adults and 3–6 mg per kilogram in children. This is generally spread out as 3-4 pills taken throughout the day. The various forms of treatment are not without possible adverse side effects. Iron supplementation by mouth commonly causes negative gastrointestinal effects, including constipation, nausea, vomiting, metallic taste to the oral iron and dark colored stools. Constipation is reported by 15-20% of patients taking oral iron therapy. Preparations of iron therapy that take longer to be absorbed by the small intestine (extended release iron therapy) are less likely to cause constipation. It can take six months to one year to get blood levels of iron up to a normal range and provide the body with iron stores.
Up to 15% of children ages 1–3 years have iron deficiency anemia. Mild iron deficiency anemia affects another 375 million. Iron deficiency affects up to 52% of pregnant women worldwide.The prevalence of iron deficiency as a cause of anemia varies among countries; in the groups in which anemia is most common, including young children and a subset of non-pregnant women, iron deficiency accounts for a fraction of anemia cases in these groups (25% and 37%, respectively). Iron deficiency is common in pregnant women.Within the United States, iron-deficiency anemia affects about 2% of adult males, 10.5% of White women, and 20% of African-American and Mexican-American women.A map provides a country-by-country listing of what nutrients are fortified into specified foods. Some of the Sub-Saharan countries shown in the deaths from iron-deficiency anemia map from 2012 are as of 2018 fortifying foods with iron. References
Zeglam A, Abugrara A, Kabuka M. Autosomal-recessive iron deficiency anemia, dystonia and hypermanganesemia caused by new variant mutation of the manganese transporter gene SLC39A14. Acta Neurol Belg. 2019 Sep;119(3):379-384. doi: 10.1007/s13760-018-1024-7. Epub 2018 Sep 19. PMID 30232769. External links

The Importance of Iron – From IronTherapy.Org
Interactive material on Iron Metabolism – From IronAtlas.com
Approach to chronic anemia : https://ashpublications.org/hematology/article/2012/1/183/83845/How-to-approach-chronic-anemia
Handout: Iron Deficiency Anemia – From the National Anemia Action Council
NPS News 70: Iron deficiency anaemia: NPS – Better choices, Better health – From the National Prescribing Service