If you have any iron deficiency symptoms, then you need to get your iron levels checked with a blood test. Iron deficiency anemia is not something to self-diagnose or treat. You should not take iron supplements before you confirm low iron or iron deficiency through a blood test.
If you have a positive test that indicates low iron, then investigations need to be undertaken to as to why you have low iron. This could be due to; blood loss (from heavy menstrual periods, or slow internal blood loss from some type of ulcer, cancer, polyp or hernia), a lack of iron in the diet, an inability to absorb iron (such as from celiac disease, bariatric mal-absorptive or other surgical procedures), medications (interfering with absorption), and, pregnancy (due to increased requirements for the growing baby and increased blood volume from your own stores).
These groups of people may have an increased risk of iron deficiency anemia. Women (due to menstruation), infants and children (due to extra requirements during rapid period of growth), vegetarians (if iron-rich foods are not eaten), and frequent blood donors. Interestingly if people have high iron the only way to get rid of it is through blood loss.
There are two types of iron from food, heme iron (from animal products particularly red meat, fish and poultry) and non-heme iron (from vegetarian sources such as vegetables, nuts, dried beans and grains) . If you eat animal products try to eat at least 2 servings of red meat each week, in addition to plenty of green leafy vegetables and colourful fruits and vegetables to maximise iron intake and iron absorption. Try to consume vitamin C rich foods with vegetarian products, to enhance the non-heme absorption such as having fresh fruit with your cereal will increase the uptake of the non-heme iron due to the vitamin C in the fruit. Some foods inhibit the absorption of iron, such as tea and coffee (polyphenols), phytic acids, calcium, soy and egg albumin. If you are deficient in iron it is more of an issue to be aware of restricting tea and coffee to in-between meals as the main advice here.
If iron stores are low your doctor may prescribe an iron supplement (usually with Vitamin C). You will have to take the supplement as prescribed, usually once a day, avoiding tea, coffee, and possibly milk for an hour or so around consuming the supplement. Or, if stores are very low, possible iron injections or even a blood transfusion. Increasing the heme and non-heme dietary sources of iron will help, including red meat, beans, lentils, green leafy vegetables, and vitamin C with each meal. Finding the cause of such low iron would be of utmost importance.