Sachi Health Omega-3 supplementation, testosterone, and menstrual regularity in PCOS: a double-blind randomized trial of 78 overweight women shows real hormonal change in 8 weeks
A double-blind randomized trial of 78 overweight women with PCOS: 8 weeks of omega-3 (3 g/day) lowered testosterone vs. placebo, and twice as many women had regular cycles by the end (47% vs. 23%).
Researchers in Iran ran a double-blind randomized trial on 78 overweight women with PCOS. Half took 3 grams of omega-3 a day for 8 weeks. Half took a placebo. The omega-3 group saw their testosterone drop significantly compared to placebo, and more than twice as many of them had their menstrual cycles become regular by the end of the study (47% vs. 23%). Eight weeks of a single supplement, and two of the most stubborn PCOS markers moved.
The numbers that matter
Can we actually trust this?
This one's a proper double-blind randomized controlled trial. Both the participants and the researchers were blinded to who got omega-3 vs. who got the placebo (paraffin capsules). That's the strongest design you can use for testing whether a supplement actually works, and it rules out a lot of the bias that plagues weaker studies.
The honest caveats: the sample is modest (78 women), the duration is short (8 weeks), and not everything moved. Testosterone and menstrual regularity changed significantly. SHBG (sex hormone binding globulin) and the Free Androgen Index did not. The researchers are upfront about this and note that a longer study is likely needed to see the full hormonal picture. As with the spearmint tea study we covered a few weeks ago: real hormonal changes are happening, and some markers respond faster than others.
Does this apply to you?
This study is most relevant if:
- You have PCOS confirmed by Rotterdam criteria
- You are overweight or obese (BMI 25 or higher)
- You are between 20 and 40 years old
- You experience irregular menstrual cycles (all study participants did)
We want to be honest: this study was conducted specifically on overweight/obese women in this age range. Whether the same effects would apply to women with PCOS who are at a normal BMI, or who are outside this age range, has not been tested in this trial. We're not going to stretch the findings to make them apply more broadly than the data supports.
As with any supplement, talk to your doctor before starting, especially if you're on other medications or have other health conditions.
Why this matters
Omega-3 is one of the most accessible supplements on earth. You can find it in any pharmacy, in any grocery store, in any country. It's cheap. It's well-tolerated. Millions of people already take it for heart health and inflammation without thinking twice.
This study is part of a growing body of evidence suggesting that for women with PCOS, omega-3 may also play a role in something more specific: lowering circulating testosterone and supporting menstrual regularity.
Why does that matter? Because elevated testosterone is what drives many of the most distressing PCOS symptoms: hirsutism, acne, hair thinning, mood changes. And menstrual irregularity is the symptom most women with PCOS describe as the one they can't ignore. It's the one that prompts most diagnoses in the first place. Doubling the rate at which cycles become regular in just 8 weeks is not a small thing.
What's striking is what omega-3 didn't change. SHBG, the protein that binds testosterone and keeps it inactive, didn't move. Free Androgen Index didn't significantly change either. The researchers think this is because 8 weeks isn't long enough to see those shifts, and because the underlying insulin resistance in PCOS keeps SHBG suppressed.
The takeaway isn't "omega-3 fixes PCOS." It's "omega-3 appears to move specific hormonal levers in PCOS, with real effects on the symptom women care about most: their cycles." That's worth knowing. And you don't have to get omega-3 from a capsule alone: a study of 224 women linked a Mediterranean diet rich in fish, olive oil, legumes, and nuts to lower testosterone.
If you want to try this
- The dose in the study was 3 grams per day.
That's higher than what's in most over-the-counter omega-3 capsules, which typically contain 1 gram each. To match the study, you'd take three capsules a day. Read the label carefully because what matters is the total EPA + DHA content, not just the capsule weight.
- Choose a quality source.
Omega-3 supplements vary widely. Look for ones that have been third-party tested for purity (look for IFOS or NSF certification) and that disclose their EPA and DHA content per capsule. Cheap fish oil can be rancid, which defeats the purpose.
- Think of this as a complement, not a replacement.
If you're already on medication for PCOS, omega-3 isn't a substitute. It's something you can add to your routine alongside your existing care. Bring it up with your doctor, especially if you're on blood thinners (omega-3 has mild blood-thinning properties).
- Give it longer than 8 weeks.
This study showed changes in 8 weeks, but the researchers note that SHBG and other markers may need longer to shift. If you're going to try this, commit to at least 3 months before judging whether it's working for you.
- Track it.
If you're going to add a daily supplement, track it. Log your daily dose, track your menstrual cycles, note how you're feeling. Without tracking, you'll never know whether it's making a difference for you specifically.
How Sachi can help
Sachi's supplement tracking system makes it easy to log omega-3 right alongside your other supplements, with specific doses. You can create a custom variable for omega-3 to make sure you're hitting your 3 grams a day. Set a daily reminder, track it alongside your cycle and symptoms, and over a few months you'll have a clear picture of whether it's making a difference for you.
This is exactly the kind of evidence-based, low-cost intervention Sachi is built to support. The research shows that specific hormonal markers respond. Now it's about tracking long enough to see if your symptoms do too.
A few terms, explained
- Testosterone
- The primary androgen (male hormone) that's also present in women in smaller amounts. In PCOS, testosterone is often elevated, which drives many of the most distressing symptoms: excess hair growth, acne, hair thinning, mood changes. In this study, omega-3 reduced testosterone significantly.
- SHBG (Sex Hormone Binding Globulin)
- A protein that binds to testosterone in your bloodstream, essentially neutralizing it. The more SHBG you have, the less free, active testosterone is available to drive symptoms. Women with PCOS often have low SHBG. In this study, SHBG didn't move, which the researchers attribute to the short study duration and the underlying role of insulin resistance.
- Free Androgen Index (FAI)
- The ratio of total testosterone to SHBG, used to estimate how much biologically active testosterone is circulating. It's a more sensitive marker than total testosterone alone. In this study, FAI decreased in the omega-3 group but not significantly.
- Rotterdam criteria
- The international standard for diagnosing PCOS. A woman meets the criteria if she has two of the following three: irregular ovulation, signs of excess androgens (clinical or biochemical), and polycystic ovaries on ultrasound. All participants in this study met these criteria.
Study at a glance
Reference
Nadjarzadeh A, Dehghani Firouzabadi R, Vaziri N, Daneshbodi H, Lotfi MH, Mozaffari-Khosravi H (2013). The effect of omega-3 supplementation on androgen profile and menstrual status in women with polycystic ovary syndrome: A randomized clinical trial. Iranian Journal of Reproductive Medicine , 11(8), 665–672. https://pmc.ncbi.nlm.nih.gov/articles/PMC3941370/
Cite this issue
Sachi Health. (June 2, 2026). Omega-3 supplementation, testosterone, and menstrual regularity in PCOS: a double-blind randomized trial of 78 overweight women shows real hormonal change in 8 weeks. The PCOS Brief. https://www.sachi-health.com/blog/the-pcos-brief-issue-10
Further reading from The PCOS Brief
Barrea L, Arnone A, Annunziata G, Muscogiuri G, Laudisio D, Salzano C, Pugliese G, Colao A, Savastano S (2019). Adherence to the Mediterranean Diet, Dietary Patterns and Body Composition in Women with Polycystic Ovary Syndrome (PCOS). Nutrients, 11(10), 2278. https://doi.org/10.3390/nu11102278 — Read our plain-English summary.