Low iron, or iron deficiency, is one of the most common conditions worldwide, causing weakness, fatigue, and issues with hair, nails, and skin as iron cannot be substituted by anything else and decreases physical and mental abilities. While iron comes from diet in heme and non-heme forms and supplementation is important, especially for pregnant women, as their child could suffer, it takes time to correct and side effects from supplements are possible, though heme iron is less likely to cause issues.