Understanding Iron and RLS

January 11, 2023 Iron, Diet and Management of Iron Levels The relationship between RLS and iron is complex, but research over the l...

January 11, 2023
Iron, Diet and Management of Iron Levels

The relationship between RLS and iron is complex, but research over the last two decades has increased the understanding of this relationship. It is now clear that brain iron deficiency plays a significant role in the development of RLS.

Dietary Iron

Iron intake from diet is essential for maintaining iron stores in the body. Unfortunately, the body absorbs only 10%–15% of dietary iron, and all ingested iron is not absorbed equally. Knowledge of iron sources in the diet will help people make choices that aid in the maintenance of iron stores in the body.

Dietary forms of iron are divided into two categories: heme iron and nonheme iron. Heme iron is only found in animal sources such as meat, poultry, fish and shellfish, and is easily absorbed in the gut. The body absorbs about 15%–35% of heme iron intake. To enhance the absorption of iron, foods rich in iron should be consumed with foods rich in vitamin C, such as orange juice, bell peppers and tomatoes. It is the acid environment in the stomach caused by vitamin C that helps iron absorption. Conversely, some items can impair the absorption of iron in foods. These items include the tannins found in tea and coffee, and the calcium in milk products and antacids.

Nonheme sources of iron include leafy greens, nuts, seeds, whole grains, legumes and fortified cereals. Although these foods are a source of iron, the iron they contain is not easily absorbed by the body. The percentage of nonheme iron absorbed is only 5%–12% because the human gastrointestinal tract does not readily absorb this type of iron.

Medical Conditions

Several medical conditions can further impair iron absorption in the gastrointestinal tract, leading to iron deficiency anemia, a state of low stores of iron in the body. Malabsorption of nutrients, including iron, occurs with medical conditions such as:

  • Celiac disease
  • Ulcerative colitis
  • Crohn’s disease
  • Small intestinal bacterial overgrowth
  • Irritable bowel syndrome

Iron deficiency anemia is also common during pregnancy due to increased blood volume and the need for additional iron by the mother and fetus. In addition, blood loss resulting from heavy menstrual cycles, surgery, or chronic blood loss due to peptic ulcers, hiatal hernia, polyps or cancer can cause iron deficiency anemia.

Brain Iron Deficiency and Iron Supplementation

Lack of available iron affects the brain and the dopaminergic system. Brain iron deficiency and dysfunction of the dopaminergic system play a central role in the development of RLS. That is why every individual with RLS needs to monitor their iron status and the steps they need to take to maintain their iron stores at the recommended levels. Low stores of body iron, as measured by serum ferritin levels and low serum iron saturation levels, correlate with low iron in the brain and the worsening of RLS symptoms.

RLS researchers recommend a serum ferritin measurement of 100 mcg/L or above to minimize the severity of RLS symptoms. If dietary sources of iron are insufficient to maintain iron stores in RLS patients, oral iron supplementation is the next step to help keep serum ferritin in the acceptable range. Oral iron is recommended when serum ferritin is less than 75 mcg/L, with the goal of raising serum ferritin levels to 100 mcg/L within three months of initiating therapy.

Guidelines to achieve maximum absorption of supplementary oral iron include:

  • Use ferrous sulfate 325 mg tablets with 60–65 mg elemental iron (check the bottle, as the amount varies), taken once daily with a beverage containing vitamin C or with a 250 mg tablet of vitamin C.
  • Take the oral iron at night; iron redistribution in the brain is highest during the nighttime hours and studies suggest it may be better absorbed later in the day.
  • Avoid consuming tea, coffee, products containing calcium (dairy products, antacids), and reflux medications within two hours of taking oral iron.
  • Schedule oral iron four hours before or after taking thyroid medications to maintain the effectiveness of the thyroid medication.

Intravenous (IV) iron infusion should be considered if ferritin levels of 100 mcg/L or above are not achieved after three months of oral iron therapy. In two recent randomized, double-blind, placebo-controlled studies, RLS patients with a normal hemoglobin level, serum ferritin of less than 300 mcg/L, and transferrin saturation of less than 45% were administered 1,000 mg of iron intravenously and showed improvement in their RLS symptoms. After infusion, it takes six to eight weeks to evaluate iron status and symptom improvement.

Administering IV iron to RLS patients with low serum ferritin levels will quickly raise those levels above 100 mcg/L and improve their symptoms in less time than it takes to evaluate the effects of oral iron supplementation. For individuals with low serum ferritin and a high level of symptom severity, IV iron is an important treatment consideration to ensure adequate iron stores in the body, iron distribution in the brain and better management of RLS symptoms. In patients with falsely elevated ferritin levels due to inflammation or infection, a low serum iron saturation of less than 20% may be a better indication of the need for iron supplementation.


For people with RLS, maintaining iron stores at therapeutic levels requires a close working relationship with an RLS provider who understands the connection between the level of iron stores in the body and its impact on RLS symptoms. Revision of an RLS treatment plan based on a periodic evaluation of iron tests will ensure better management of RLS symptoms and an improved quality of life.

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