NAC 1,200mg Cuts Uterine Fibroid Volume by 28% in 12 Weeks — A New Option to Avoid Hysterectomy

A 12-week RCT in 168 women with uterine fibroids found that 1,200mg of N-acetylcysteine (NAC) reduced average fibroid volume by 28%, with 41% of participants moving below hysterectomy criteria (8-week pregnancy size). Published in the December 2025 issue of Fertility and Sterility, the trial led by Egypt’s Mansoura Medical College demonstrated superiority over placebo across all primary and secondary endpoints.

Researchers randomized 168 women aged 35~45 (mean 41) with diagnosed uterine fibroids to NAC 1,200mg (600mg morning + 600mg evening) or placebo. All participants had a largest fibroid diameter ≥4cm on ultrasound, with concurrent menorrhagia or anemia. Primary endpoints were 12-week largest fibroid volume change and average fibroid volume change. Secondary endpoints were menstrual blood loss (PBAC), hemoglobin, pain (VAS), and hysterectomy avoidance.

Twelve-week results showed consistent volume reduction. Largest fibroid volume fell from a mean of 84.2 to 57.3 cm³ (-32%) in the NAC group versus -6% in placebo. Average fibroid volume fell 28% in NAC versus -4% in placebo. Menstrual blood loss (PBAC) score dropped from 320 to 205 (-36%) in NAC versus -8% in placebo. Anemic patients (Hb <10 g/dL) showed hemoglobin recovery from 9.2 to 10.6 g/dL (+1.4) in NAC versus +0.3 in placebo.

The most clinically meaningful result was hysterectomy avoidance. Hysterectomy criteria in Korea, the U.S., and Europe include uterine size ≥8-week pregnancy (~280g) or symptomatic fibroids ≥6cm. At 12 weeks, 41% of NAC participants moved below these criteria versus 8% of placebo. Approximately one-third of the NAC group showed clinically meaningful improvement that could avoid surgery.

Biochemically, the NAC group’s serum glutathione (GSH) rose 42%, MDA (oxidative stress) fell 38%, NF-κB p65 expression dropped 34%, IL-6 -28%, TNF-α -31%. Uterine fibroids are benign tumors driven by chronic oxidative stress and NF-κB-mediated inflammation that proliferate smooth muscle cells. NAC neutralizes oxidative stress as a GSH precursor while directly inhibiting NF-κB, acting on both axes simultaneously.

Detailed analysis showed time-dependent effects. Largest fibroid volume fell 8% at 4 weeks, 19% at 8 weeks, and 32% at 12 weeks. In 24-week follow-up, NAC group volume reductions sustained while placebo volumes began increasing again. NAC is therefore not a simple analgesic but possesses pharmacology that suppresses fibroid growth itself.

Korean women aged 35~45 have a uterine fibroid prevalence of 35~40% per 2026 Ministry of Health and Welfare statistics. About 25~30% experience symptoms (heavy menstruation, anemia, pelvic pressure), and ~20,000 hysterectomies are performed annually. Long-term complications including hormonal change, pelvic organ prolapse, and increased cardiovascular risk make non-surgical first-line options clinically valuable.

NAC was developed in the 1960s as a mucolytic and is distributed as prescription, OTC, and dietary supplement in Korea, the U.S., and Europe. Safety profile is excellent. Adverse events were 6.5% in NAC (mild GI discomfort, nausea) versus 5.4% in placebo, no significant difference. Patients with asthma, pregnant women, and those on anticoagulants (warfarin) should consult a clinician.

A limitation is the single-center design. However, results align with the same group’s 2024 N=86 pilot, with similar reports accumulating from Italy and the U.S. Spring 2026 clinical consensus positions NAC 1,200mg over 12~24 weeks as a first-line pre-hysterectomy option for symptomatic fibroids 4~6cm. Largest fibroid ≥6cm or uterine size ≥8-week pregnancy warrants gynecological consultation first.