--- title: Krill oil and PMS: evidence, dosing, and side effects description: Krill oil and PMS: see what trials and a meta-analysis found, typical doses, how long it takes to work, side effects, and who should skip it. url: https://niyora.com/treatments/omega-3-for-pms/ --- - [Niyora](https://niyora.com/) - [Treatments](https://niyora.com/treatments/) - Krill oil and PMS: does it work? Treatments # Krill oil and PMS: does it work? Krill oil has one small randomized trial behind it for PMS, and it eased symptoms and period pain somewhat more than fish oil over three cycles. A broader review of omega-3 trials found a real benefit for PMS overall, but the krill oil evidence specifically is thin and hasn't been tested against a placebo. Updated 14 October 2026 Niyora editorial Mixed evidence Strength of evidence Mixed Trials disagree, or the effect is small. - None - Limited - Mixed - Moderate - Strong ## At a glance - Krill oil has one small controlled trial behind it for PMS (n=70, 2003), comparing it to fish oil rather than a placebo. - A 2022 meta-analysis of omega-3 trials for PMS found a real reduction in symptom severity overall, though the studies varied widely. - Benefits showed up over two to three menstrual cycles in the krill oil trial, not after a single month. - Side effects are usually mild: a fishy aftertaste, burping, or loose stools. - Check with a doctor first, or skip it, if you have a shellfish allergy or take blood thinners. ## Strength of evidence Mixed evidence - None - Limited - Mixed - Moderate - Strong Only one small randomized trial has tested krill oil itself for PMS, comparing it to fish oil rather than a placebo. A broader meta-analysis of omega-3 trials found a genuine benefit, but the studies pooled varied widely in dose and length, so treat the krill oil evidence as promising, not settled. ## Does krill oil help PMS symptoms? Maybe, a little. Here's what the evidence shows so far: - One small randomized trial found that krill oil eased PMS symptoms and period pain over three menstrual cycles, working somewhat better than plain fish oil (2003, Alternative Medicine Review, n=70). - A pooled analysis of omega-3 trials for PMS found a real drop in symptom severity overall (2022 meta-analysis, Journal of Obstetrics and Gynaecology Research). That's the honest shape of the evidence. Omega-3 fats as a group have decent support behind them. Krill oil on its own has just one controlled trial, and that trial compared it to fish oil rather than to a placebo. If you want the fuller picture on omega-3 and PMS before you decide what to try, [omega-3 for PMS](https://niyora.com/treatments/omega-3/) covers the wider research. If your pattern of symptoms sounds more severe than typical PMS, with mood changes that take over a week every month, the dosing and evidence picture is different: see omega-3 for PMDD. Where this sits in your cycle PMS window The week before your period Day 1 Ovulation Day 28 ## What does the research say? Here's what the three most relevant studies found, side by side. | Study | Design | What it found | | --- | --- | --- | | Krill oil trial, 2003 (n=70) | Double-blind RCT, krill oil vs fish oil, three cycles | Both groups improved, but the krill oil group used fewer pain relievers for cramps than the fish oil group | | Omega-3 meta-analysis, 2022 | Pooled RCTs of omega-3 for PMS | Omega-3 reduced PMS severity overall, with a large average effect, though results varied a lot between studies | | Krill oil blend pilot, 2013 (n=29) | Open-label pilot, krill oil plus added vitamins, no placebo group | Women reported less anxiety, bloating, and mood swings after three months of daily use | The meta-analysis is the strongest piece of this picture. It pooled randomized trials and found that omega-3 **reduced PMS severity** overall, for both physical and emotional symptoms. The studies varied widely in dose, length, and who took part, so the exact size of the effect stays fuzzy. Read the krill oil pilot with some caution. It had no placebo group, so part of what women felt could reflect the general experience of being tracked and cared for during a trial, not the oil itself. For more on how we weigh evidence like this, see [PMS and PMDD research, summarised](https://niyora.com/research/). Right now What helps in the moment - 1 Name it in one sentence: this is PMS, not something wrong with you. - 2 If you're mid-fight, say you need 20 minutes and that you'll come back, then leave the room. - 3 Breathe out for six counts, several times, before you decide what to say or do next. - 4 Write down what happened while it's fresh, so you can look at it clearly once the wave passes. - 5 Niyora is a PMS and PMDD support app. Its Moon feature lets you write what happened, see it another way, and draft a reply to hold before sending. Niyora walks you through this when it happens: - Calm down - - See it another way - - Choose what to say ## How long does it take to work? In the krill oil trial, differences from baseline showed up by day 45 and grew by day 90, about two to three menstrual cycles of daily use. The 2022 meta-analysis found that longer treatment tracked with bigger drops in symptom severity, based on a meta-regression of age and treatment duration across the pooled trials. That points to one practical rule: **give it three full cycles** before deciding it isn't working. PMS symptoms already swing from month to month, so judging after a single cycle makes it hard to tell a real effect from normal variation. Stopping and restarting partway through a cycle muddies the picture further, so pick a start date and stick with it for the full trial period. If you're tracking what changes, a [daily symptom chart](https://niyora.com/tools/drsp-chart/) makes the pattern easier to see than memory alone. ## What are the side effects? Across the trials, krill oil was generally well tolerated. The side effects reported were mild and mostly digestive. - A fishy aftertaste or mild burping after taking it - Occasional stomach upset or looser stools, especially in the first week or two - Neither published study reports any serious side effects, though safety monitoring wasn't the stated focus of either trial Taking it with food tends to cut down on the aftertaste and nausea some people notice. Compared with plain fish oil in the same trial, krill oil wasn't reported as causing more side effects, so it may not solve fishy burping if that's what's put you off fish oil before, since krill oil can carry a similar fishy aftertaste even though krill itself is a crustacean, not a fish. If stomach upset doesn't settle after a week or two, that's a reasonable point to stop and try a different product or dose. ## Who should avoid it? Krill oil isn't right for everyone. A few situations call for extra caution: - You have a seafood or shellfish allergy. Krill is a small crustacean, and reactions are possible even if fish itself sits fine with you. - You take blood thinners or have a bleeding disorder. Omega-3 oils, including krill oil, can add a mild blood-thinning effect. - You're pregnant or breastfeeding. Supplement safety in pregnancy needs a conversation with your own provider, not a general answer. - You're already taking a fish oil or omega-3 supplement. Doubling up hasn't been shown to add extra benefit, just extra capsules and cost. Tracking on a [daily symptom chart](https://niyora.com/tools/drsp-chart/) for two cycles gives you and a doctor the same picture to work from. When to see a doctor If PMS takes over a week of every month to pass, or krill oil hasn't helped after three full cycles, see a GP or gynecologist and bring two months of daily notes. ## What else helps alongside it? Krill oil is one piece, not a whole plan. A 2024 review of diet and PMS found that eating patterns low in simple carbohydrates, added fat, salt, and alcohol, and higher in fresh food rich in B vitamins, vitamin D, zinc, and calcium, tracked with milder PMS. None of that replaces treatments with stronger evidence behind them for more severe symptoms, like certain SSRIs taken only in the days before your period, some hormonal contraceptives, or CBT. A doctor decides which of those fits you, based on how severe things get and your own health history. For the wider list of what actually has evidence behind it, from lifestyle changes to prescription options, see [PMS treatment: what actually helps](https://niyora.com/treatments/pms-treatment/). And if you're still working out whether what you're feeling counts as PMS at all, [what is PMS](https://niyora.com/premenstrual-syndrome/) walks through how it's defined. From the research library ## Research on omega-3 21 studies in the library look at omega-3 in PMS and PMDD. They were published from 1988 to 2026, and each one has a short summary of what was tested and found. 21 studies, 1988 to 2026 How strong the studies are Strong study design 1 Moderate study design 6 Early or limited evidence 14 - [Randomised trial, 2003What complementary and alternative medicines help with women's reproductive health issues?Acupressure helps with pregnancy nausea and calcium helps with PMS. Vitamin B6, ginger, magnesium, chaste-tree berry, low-fat diet, exercise, and fish oil show promise but need more research.Strong study design](https://niyora.com/research/papers/complementary-and-alternative-medicine-cam-in-reproductive-age-women-a-review-of-2003/) - [Review, 2026Can diet and nutrition help reduce PMS symptoms?Yes. High intake of calcium, magnesium, vitamin D, and vitamin B6 reduce PMS symptoms. A high-fiber, low-sugar diet with omega-3 fatty acids also appears helpful.Moderate study design](https://niyora.com/research/papers/exploring-the-role-of-diet-in-alleviating-symptoms-of-premenstrual-syndrome-pms-2026/) - [Systematic review, 2022Do omega-3 supplements help reduce PMS?Yes, omega-3 fatty acids appear to reduce PMS severity overall and specifically reduce both body-related and mood-related symptoms. The benefit increased with longer treatment duration.Moderate study design](https://niyora.com/research/papers/effect-of-omega-3-fatty-acids-on-premenstrual-syndrome-a-systematic-review-and-2022/) - [Non-randomised trial, 2020What treatments help premenstrual syndrome?Both medications and non-drug treatments help PMS. Non-drug options including herbs, supplements, exercise, and therapy are recommended as they have fewer side effects.Moderate study design](https://niyora.com/research/papers/evaluation-of-non-pharmacological-strategies-therapeutic-and-cognitive-2020/) - [Randomised trial, 2018Does omega-3 fish oil help with premenstrual symptoms?Possibly. Most premenstrual symptoms improved significantly, and women in the omega-3 group showed improvement in quality of life, though the placebo group also improved.Moderate study design](https://niyora.com/research/papers/the-effect-of-omega-3-fatty-acid-supplementation-on-premenstrual-syndrome-and-2018/) - [Randomised trial, 2014Which supplement works best for PMS - vitamin E, vitamin B6, calcium, or omega-3?All four supplements and placebo reduced symptom severity over 3 months. The study does not specify which was most effective.Moderate study design](https://niyora.com/research/papers/comparison-of-the-effect-of-vit-e-vitb6-calcium-and-omega-3-on-the-treatment-of-2014/) [See all 21 studies on omega-3 fatty acids](https://niyora.com/research/topics/treatment-omega-3/) ## Questions people ask Does krill oil help with PMS symptoms? + A small trial of 70 women found krill oil eased PMS symptoms and period pain over three menstrual cycles, working somewhat better than plain fish oil. That's encouraging, but it's one study, and no trial has yet compared krill oil against a placebo for PMS specifically. Is krill oil better than fish oil for PMS? + In the one trial that compared them directly, women taking krill oil needed fewer pain relievers for cramps than those taking fish oil, though both groups reported improvement overall. That's a single data point, not a pattern confirmed across multiple studies, so treat it as an early lead. How long before krill oil helps PMS symptoms? + In the controlled krill oil trial, differences from baseline showed up by day 45 and grew by day 90, roughly two to three menstrual cycles. A separate meta-analysis of omega-3 trials found longer use tracked with bigger improvements, so give it a few cycles before judging whether it's working. What are the side effects of krill oil? + Trials reported krill oil as generally well tolerated, with the most common complaints being a fishy aftertaste or mild stomach upset. No serious side effects turned up in either study. If you take blood thinners, that's worth knowing before you start, since omega-3 oils can mildly thin blood. Can I take krill oil alongside other PMS treatments? + Krill oil isn't a substitute for treatments with stronger evidence, like certain SSRIs used only before your period, some hormonal contraceptives, or CBT, which a doctor can discuss with you. A 2024 review also linked PMS severity to diet, so food choices sit alongside any supplement, not instead of it. ## Sources - 1. [Evaluation of the effects of Neptune Krill Oil on the management of premenstrual syndrome and dysmenorrhea](https://pubmed.ncbi.nlm.nih.gov/12777162/), Alternative medicine review : a journal of clinical therapeutic, 2003 - 2. [An open-label pilot study to assess the effectiveness of krill oil with added vitamins and phytonutrients in the relief of symptoms of PMS](https://doi.org/10.2147/nds.s48133), Nutrition and Dietary Supplements, 2013 - 3. [Effect of omega-3 fatty acids on premenstrual syndrome: A systematic review and meta-analysis](https://doi.org/10.1111/jog.15217), The journal of obstetrics and gynaecology research, 2022 - 4. [Relationships between Premenstrual Syndrome (PMS) and Diet Composition, Dietary Patterns and Eating Behaviors](https://doi.org/10.3390/nu16121911), Nutrients, 2024 Ask AI about this page Copy prompt ChatGPT ↗ Claude ↗ Perplexity ↗ Google AI Mode ↗ Grok ↗ On this page - [Does krill oil help PMS symptoms?](#does-krill-oil-help-pms-symptoms) - [What does the research say?](#what-does-the-research-say) - [How long does it take to work?](#how-long-does-it-take-to-work) - [What are the side effects?](#what-are-the-side-effects) - [Who should avoid it?](#who-should-avoid-it) - [What else helps alongside it?](#what-else-helps-alongside-it) - [Research](#research) - [Questions](#faq) Niyora PMS & PMDD support For the hard moment before your period. Private, no account. [Get it on iPhone](https://apps.apple.com/app/niyora-pms-emotions/id6764561688) ## Keep reading Treatment Omega-3 and evening primrose oil for PMS: what the trials found Treatment PMS treatment: what actually helps Condition What is PMS? Premenstrual syndrome, explained Care guide Finding a PMDD specialist Guide All 26 research findings