Iron for Restless Legs Syndrome
For restless legs syndrome, iron works when iron stores are depleted, and intravenous ferric carboxymaltose (FCM) is the best-supported form. It is now a guideline first-line option once serum ferritin is at or below 75 ng/mL (or transferrin saturation under 20%), but it is not a cure-all and should follow a blood test rather than self-treatment.
Why this grade7-layer evidence engine
The grade reflects consistent randomized evidence for a specific scenario rather than a blanket effect. A multicenter RCT of IV FCM (PMID 38625730, n=209) cut IRLS symptom scores more than placebo (LS-mean -8.0 vs -4.8; p=0.0036), and two meta-analyses agree: PMID 39326219 (n=537) found a pooled -6.03-point reduction (p=0.004), and the 2025 review PMID 40821477 (12 RCTs, n=511) found -5.28 points overall with a responder rate roughly doubled (RR 2.06).
It lands at moderate rather than strong because the benefit is uneven and partly partial. In the same large RCT the global-impression responder rate was not significantly better than placebo (35.5% vs 28.7%; p=0.30). Effect also depends on formulation: IV FCM is robust (subgroup -6.37; p=0.001) while iron sucrose did not reach significance (p=0.24) in PMID 40821477, and oral ferrous sulfate is only conditionally recommended in the 2025 AASM guideline (PMID 39324694).
Regulators and clinics support iron as essential (NIH ODS, FDA, EFSA, WHO), and specialty bodies are explicit for RLS: Mayo and Cleveland Clinic link low (especially brain) iron to symptoms, and the AASM/IRLSSG position recommends iron first-line when ferritin is at or below 75 ng/mL. Crucially, this is conditional on iron status, so fasting morning ferritin and TSAT testing should come first; the NHS notes most people get enough iron from diet, and unguided supplementation risks overload (e.g., hemochromatosis).
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditable▸View the full decision path (audit trail)
- compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.743
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高階證據未達主導 (1 positive vs 1 negative)，由 raw_score 決定
- tier_strict_requirement_check — Tier 條件達標，未降階
- detect_disputes — 偵測到 0 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status