Iron and Restless Legs: Ferritin Targets, Oral vs IV Iron
Written and medically reviewed by Matthew Viereck, MD, board-certified sleep medicine physician · Reviewed October 2026 · Editorial standards
Chapters
- 0:00Disclaimer
- 0:10Iron and restless legs
- 0:19Four questions
- 0:39Why brain iron matters
- 1:10The normal blood test problem
- 1:38The two tests: ferritin and TSAT
- 2:09Testing it right
- 2:43The numbers: 2025 guideline
- 3:20A wider window, and a firm limit
- 3:58Test first, and look for a cause
- 4:27Iron by mouth
- 5:12When infusion is preferred
- 5:40Which IV iron
- 6:12What to expect with an infusion
- 6:54Iron is the foundation
- 7:21Three things to remember
About this video
Iron is one of the most important things to check in restless legs syndrome (RLS), and the numbers that matter are not the ones on a standard lab report. The leading explanation is that the brain does not get or use enough iron in areas that help control movement, and routine blood tests are only indirect markers of brain iron. That is why RLS has its own, higher iron targets.
We cover why brain iron matters, the two blood tests that guide treatment (ferritin and transferrin saturation, or TSAT), how to get an accurate result, the treatment thresholds in the 2025 American Academy of Sleep Medicine guideline (ferritin at or below 75 or TSAT below 20 percent; infusion only between 75 and 100), the wider window for IV iron in the 2026 expert algorithm (ferritin 75 to 300 with TSAT below 45 percent), how to take iron by mouth so more of it is absorbed (every other day, away from food, with vitamin C), when an infusion is preferred, which IV iron forms are used, and what to expect.
The most important message: do not start iron on your own. Too much iron is harmful. Test first, and decide with your clinician.
Transcript
Show
0:00Disclaimer
This video is for educational purposes only and is not medical advice. Please talk with your own clinician before starting iron or changing any treatment.
0:10Iron and restless legs
If you have restless legs, iron may be the most important thing to check. And the numbers that matter are not the ones printed on a standard lab report.
0:19Four questions
We will cover four things. Why brain iron matters. The two blood tests that guide treatment, and the numbers we use. Iron by mouth versus iron by infusion. And what to expect. One message will come up more than once: do not start iron on your own. Test first, and decide with your clinician.
0:39Why brain iron matters
Restless legs syndrome is an urge to move the legs, often with an uncomfortable feeling, that is worse at rest and in the evening. Its link with iron has been known for decades. The leading explanation today is that the brain does not get or use enough iron, especially in deep areas that help control movement. Iron supports the dopamine system there, the chemical messenger system involved in movement. So the goal of iron treatment in restless legs is not just to fix the blood. It is to get more iron into the brain.
1:10The normal blood test problem
Here is the part that surprises most people. We cannot measure brain iron in an everyday clinic, so we rely on blood tests as indirect markers, and blood iron levels do not reliably reflect iron levels in the brain. Most people with restless legs have blood iron results inside the normal lab range, and many of them still benefit from iron. That is why restless legs has its own, higher iron targets. A normal routine panel does not rule out an iron problem.
1:38The two tests: ferritin and TSAT
The 2025 guideline from the American Academy of Sleep Medicine says everyone with clinically significant restless legs should have iron studies, checked regularly over time. Two numbers matter most. Ferritin is a protein that stores iron; its blood level reflects your iron reserves, like a savings account. Transferrin saturation, often shortened to TSAT, is the share of the blood's iron carrying protein that is actually carrying iron. Think of it as the iron in transit right now.
2:09Testing it right
How the blood is drawn changes the result. Test in the morning, fasting. Avoid iron pills and iron fortified foods for at least a day beforehand; the 2026 expert algorithm suggests stopping iron pills for two days. And know that ferritin also rises with infection and inflammation, so it can look falsely reassuring. If you are sick, or an inflammatory condition is flaring, ask whether the test should wait until you are well. When inflammation is ongoing, a transferrin saturation below twenty percent is the more reliable sign of low iron.
2:43The numbers: 2025 guideline
Now the numbers. Under the 2025 guideline, iron treatment is recommended when ferritin is at or below seventy five micrograms per liter, or transferrin saturation is below twenty percent. That can be iron by mouth or by infusion. That is well above many labs' cutoff for normal. A ferritin of forty may be fine for the general population and still too low for restless legs. Between seventy five and one hundred, the guideline says to use infusion only, because the gut absorbs very little iron once stores reach that level. For children, the threshold is a ferritin below fifty.
3:20A wider window, and a firm limit
A newer expert algorithm, published in 2026, goes further. It says infusion should be considered for chronic, persistent restless legs when ferritin is anywhere from seventy five up to three hundred, as long as transferrin saturation is below forty five percent. Newer studies suggest people in that range respond about as well as those with lower levels. There is also a firm limit. Iron should not be given when transferrin saturation is above forty five percent. A result that high, more than once, should prompt testing for hemochromatosis, an inherited condition in which the body stores too much iron.
3:58Test first, and look for a cause
That is why iron should never be taken just in case. Iron is not a harmless vitamin. Without testing, it can quietly overload someone with undiagnosed hemochromatosis. And if your ferritin is truly low, below the normal range for your age and sex, your clinician should also look for the reason. Common causes include heavy menstrual periods, bleeding from the stomach or bowel, a vegan diet, frequent blood donation, and acid reducing medicines that block iron absorption.
4:27Iron by mouth
When iron by mouth is the right choice, a few details make it work better. A typical dose is about sixty five milligrams of elemental iron, the amount in one standard ferrous sulfate tablet. Take it no more than once a day, and preferably every other day. That sounds backwards, but each dose blocks absorption of the next for about two days. An evening dose may work better, since animal research suggests iron moves into the brain more at night. Take it at least two hours away from food, calcium, magnesium and caffeine, and consider one hundred to two hundred milligrams of vitamin C with each dose. If your stomach objects, taking it with food is an acceptable trade. Iron by mouth is slow; ferritin and symptoms are rechecked after about three months.
5:12When infusion is preferred
Infusion, also called IV iron, goes straight into a vein and skips the gut entirely. Besides the higher ferritin range we just covered, infusion is used when ferritin is below seventy five and the gut cannot absorb iron well, for example with bowel disease or after weight loss surgery; when iron pills cause side effects you cannot live with; when three months of pills have not helped; or when symptoms are severe enough that a faster response is needed.
5:40Which IV iron
Not all IV iron is the same. The preferred forms release iron slowly, which seems to help more of it reach the brain. The 2025 guideline gives a strong recommendation to ferric carboxymaltose, the best studied, and a conditional recommendation to low molecular weight iron dextran and to ferumoxytol. The 2026 algorithm adds ferric derisomaltose to that slow release group. Iron sucrose, a faster release form, did not show a clear benefit in restless legs studies, except in people on dialysis.
6:12What to expect with an infusion
What to expect with an infusion. It is given in an infusion center or similar setting, though serious allergic reactions are rare, about one in two hundred thousand. Mild reactions like facial flushing are handled by pausing and slowing the drip. Antihistamines are not recommended beforehand, since they can worsen restless legs. Ferric carboxymaltose lowers blood phosphate in roughly forty to seventy percent of adults, usually without symptoms. Be patient: relief can take six to eight weeks, so with severe symptoms your clinician may adjust other treatment at the same time. If symptoms come back months later, a repeat infusion can be considered after new labs.
6:54Iron is the foundation
Iron is the foundation, not the whole house. Alongside iron, the guideline starts with removing things that aggravate restless legs: alcohol, caffeine, sedating antihistamines, many antidepressants, and untreated sleep apnea. If symptoms still need treatment, the preferred medicines are gabapentin, gabapentin enacarbil and pregabalin. Our video on augmentation explains why dopamine medicines are no longer the first choice.
7:21Three things to remember
Three things to remember. Restless legs is often a brain iron problem, even when routine blood tests look normal. Iron treatment starts when ferritin is at or below seventy five or saturation is below twenty percent, and infusion can make sense at higher levels. And test first; never start iron on your own. This video is not medical advice; talk with your own clinician about your iron and your treatment. The full article, with every reference, is at bettersleepproject.com. Thank you for watching.
References
- Winkelman JW, Berkowski JA, DelRosso LM, et al. Treatment of restless legs syndrome and periodic limb movement disorder: an American Academy of Sleep Medicine clinical practice guideline. J Clin Sleep Med. 2025;21(1):137-152.
- Allen RP, Picchietti DL, Auerbach M, et al. Evidence-based and consensus clinical practice guidelines for the iron treatment of restless legs syndrome/Willis-Ekbom disease in adults and children: an IRLSSG task force report. Sleep Med. 2018;41:27-44.
- Silber MH, Berkowski JA, Buchfuhrer MJ, et al. An updated algorithm for the management of restless legs syndrome. Mayo Clin Proc. 2026;101(9):1561-1588.
- Connor JR, Boyer PJ, Menzies SL, et al. Neuropathological examination suggests impaired brain iron acquisition in restless legs syndrome. Neurology. 2003;61(3):304-309.
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Medical Disclaimer: This video is based on published sleep research and is provided for general education. It is not medical advice. Talk with your own clinician before starting, stopping or changing any treatment. Read full disclaimer.