Tool
Omega-6 to omega-3 ratio
The ratio moves reliably when you take a supplement, and the disease activity scores don't move along with it at all. That gap between the marker and the outcome is what this page is about. It's also why the page reads more cautiously than most of what gets written about fish oil.
What the research found.
One review pooled randomized trials in rheumatoid arthritis, where omega-3 supplements lowered the omega-6 to omega-3 ratio. The pooled effect was minus 1.06, with the true value sitting somewhere from minus 1.39 to minus 0.73. That came in at a P value well below 0.001.
In that review, three other measures fell only slightly, and those three are the sedimentation rate, C-reactive protein, and the DAS28 disease activity score. Not one of the three reached statistical significance. Every P value among them came in above 0.05, which is where the field draws its line.
Marine oil supplements lowered arthritis pain across 22 separate rheumatoid arthritis trials in one pooled review. The pooled effect was minus 0.21, and its upper limit was minus 0.004, which barely misses no effect at all. Function didn't change across those trials, coming in at minus 0.01.
The omega-3 index rose with the dose in the paper that first proposed it. Half a gram a day took it from 4.7 percent to 7.9 percent, one gram took it to 9.9 percent, and two grams took it to 11.6 percent. Those are figures about blood rather than about joints.
This calculator does not diagnose anything. It puts a number in context. What the number means for you is a conversation with your clinician.
What the ratio is, and what it responds to
The omega-6 to omega-3 ratio compares two families of fat in your blood, and the argument for measuring it runs like this. Modern diets supply far more omega-6 than omega-3, the two compete for the same enzymes, and the balance between them affects how readily your body makes inflammatory signals. That's a sound mechanism, and it's why the ratio gets the attention it does.
The ratio also responds to a supplement just as you'd predict it would. One review pooled randomized trials in rheumatoid arthritis, where omega-3 supplements lowered the ratio at a pooled effect of minus 1.06, EPA rose at 0.74, and DHA rose at 0.62, all three at P values below 0.001. If the question is whether fish oil changes your fat readings, the answer is a clear yes.
The interesting part is what happened to the disease in those trials. Three measures fell only slightly, and those are the sedimentation rate, C-reactive protein, and the DAS28 disease activity score. None of the three reached significance, so the marker moved and the disease behind it didn't follow.
Where the 8 percent target came from
A 2004 paper proposed the omega-3 index as a risk marker and estimated the values that would count. An index at or above 8 percent went with the most protection, and an index of 4 percent or below went with the least. The authors were clear about what they had done, which was an informed estimate from the data in front of them rather than a threshold set by a trial.
Every one of those data sources was a heart study, and the outcome throughout was death from coronary heart disease. That's a real question and it isn't this one. No rheumatic outcome fed into the 8 percent figure, and no trial in rheumatoid arthritis, lupus, spondyloarthritis, or any other rheumatic disease has aimed anyone at an index target.
So quoting 8 percent as a goal for inflammatory arthritis moves a number across questions. It was built for one outcome and it's being used for another. The dose response from that paper is worth knowing for context, and the index rose from 4.7 percent to 7.9 percent on half a gram a day, reached 9.9 percent on one gram, and reached 11.6 percent on two. Those figures describe what the supplement does to blood rather than what it does to a joint.
What fish oil does do in inflammatory arthritis
The honest summary is short enough to give in one line. The effect is small, it's real on pain, and it's absent on function. One review pooled marine oil trials across arthritis diagnoses, where pain fell at a pooled effect of minus 0.24 overall and at minus 0.21 across the 22 rheumatoid arthritis trials.
That rheumatoid arthritis result has an upper limit of minus 0.004, which sits about as close to no effect as a significant finding can sit. Function tells the other half of the story, because across those trials the effect on function was minus 0.01. That's nothing at all, and an effect on pain with no effect on function is a real finding rather than a contradiction.
The tender joint count did fall in the rheumatoid arthritis review, and that result reached significance. It's worth knowing why it counts for less than it looks like it should. Tender joint count is the softest part of the DAS28 score, it's the part most likely to move on hope alone, and most of the trials were small and either open or poorly blinded.
When the softest measure moves and the hard ones don't, that direction of travel tells you something. It doesn't tell you the supplement is useless. It tells you the effect is sitting at the soft end of what gets measured, which is where a small real effect and a placebo effect look alike.
What to do with this if you take fish oil
Nothing here is an argument for stopping something that helps you, because a small effect on pain is still an effect. The safety record of fish oil at ordinary doses is reasonable, and the wider heart argument stands on its own in a group whose heart risk is raised. So if you take it and you feel better on it, that's a fair place to be.
What the evidence doesn't support is chasing a blood level. Every trial in this field gave a dose and measured what happened, and none aimed anyone at an index target. A measured index doesn't connect to any tested action in rheumatic disease, so paying for repeat testing to chase 8 percent buys you a number rather than a benefit.
The useful question to ask before you spend anything is what you're hoping to move. If it's pain, the evidence gives you a small effect and this page has the size of it. If it's your disease activity score, your sedimentation rate, or your C-reactive protein, the trials say those didn't move, and being clear about which one you're after makes the decision much easier.
Common misconceptions.
Myth. An omega-3 index of 8 percent is the target.
Reality. It's the target for a different outcome altogether, and that's the whole objection. The figure was estimated from deaths from coronary heart disease, using data that came from heart studies, and its own authors called it an informed estimate rather than a measured threshold. No rheumatic outcome fed into it, and no trial has aimed anyone at reaching it since.
Myth. Lowering the ratio treats the inflammation.
Reality. It lowers the ratio, which is a different statement from treating the inflammation. Across trials in rheumatoid arthritis the supplement moved the fatty acid readings it was meant to move, and it left three other measures unchanged. Those three are the sedimentation rate, C-reactive protein, and DAS28, and that's what a stand-in looks like when it comes apart from the outcome.
Myth. Fish oil doesn't do anything for arthritis.
Reality. That overstates it in the other direction, and the truth sits between the two. Pain fell across 22 rheumatoid arthritis trials, at a pooled effect of minus 0.21, and that result is real and reached significance. It's also small and fragile, with an upper limit sitting at minus 0.004, and function didn't change at all.
Myth. I should get my omega-3 index tested to guide treatment.
Reality. No trial anywhere dosed to an index target, and that holds in rheumatic disease and outside it. Every trial in the two reviews gathered here gave a dose of EPA and DHA and then measured what happened next. So the evidence supports choosing a dose, and it doesn't support chasing a blood level.
Questions patients ask.
Where does the 8 percent omega-3 index target come from?
From deaths from coronary heart disease, which is not the question anybody on this site is asking. A 2004 paper proposed the marker after looking at heart studies, where an index at or above 8 percent went with the most protection and an index of 4 percent or below went with the least. The authors said openly that this was an informed estimate from the data in front of them, and nobody has aimed patients at it since.
Does a supplement change the ratio?
Reliably, and that's the least interesting thing a supplement does. One review pooled trials in rheumatoid arthritis, where the omega-6 to omega-3 ratio fell at a pooled effect of minus 1.06, EPA rose at 0.74, and DHA rose at 0.62, all three with P values below 0.001. The chemistry does what it's meant to do, and the question is what follows from it.
So does it improve the arthritis?
Barely on the softest measure, and not at all on the harder ones. In that review the tender joint count fell and reached significance, while three other measures didn't, and those three are the sedimentation rate, C-reactive protein, and DAS28. Tender joint count is the part of that score most likely to move on hope alone, and most of the trials were small and poorly blinded.
Should I have my omega-3 index measured?
No trial tells you what to do with the result in rheumatic disease. Every trial in this field gave a dose of EPA and DHA rather than aiming anyone at a blood level, so a measured index doesn't connect to any action somebody has tested. If you want a reason to measure it, that reason has to come from heart risk, which is where the marker was built in the first place.
What dose did the trials use?
That varied a great deal between trials, which is one reason the pooled effects are so mixed. The paper that proposed the index reported its own dose response, where half a gram a day raised it from 4.7 percent to 7.9 percent, one gram reached 9.9 percent, and two grams reached 11.6 percent. Those are figures from a heart paper rather than a rheumatology dose, and this site won't turn them into one.
Is it better to change the ratio through food?
Food gets you the rest of what comes with oily fish, and no trial here compared food against capsules on any rheumatic outcome. What's fair to say is that the trials tested capsules, so the evidence we have describes capsules. Eating oily fish is worth doing for wider reasons than this ratio, and framing it as a way to hit a number oversells what the number can do.
Why does this page sound so discouraging?
Because the honest form is less exciting than the marketed one, and you deserve the honest form before you spend money. Fish oil has a small, real effect on pain in rheumatoid arthritis, no shown effect on disease activity scores, and none on function either. That's a modest place to land, and it's still more useful than a target borrowed from cardiology.
References.
- Wang W; Xu Y; Zhou J et al. Effects of omega-3 supplementation on lipid metabolism, inflammation, and disease activity in rheumatoid arthritis: a meta-analysis of randomized controlled trials. Clinical Rheumatology. 2024;43:2479-2488. 10.1007/s10067-024-07040-0Meta-analysis of 18 randomised controlled trials
- Senftleber NK; Nielsen SM; Andersen JR et al. Marine Oil Supplements for Arthritis Pain: A Systematic Review and Meta-Analysis of Randomized Trials. Nutrients. 2017;9. 10.3390/nu9010042Systematic review and meta-analysis of randomised trials
- Harris W; von Schacky C. The Omega-3 Index: a new risk factor for death from coronary heart disease?. Preventive Medicine. 2004;39:212-220. 10.1016/j.ypmed.2004.02.030Narrative proposal deriving a new risk marker from previously published observational studies and secondary-prevention trials
This page gathers the published research on this subject into one place. The studies behind it were published between 1989 and 2026, and every figure links to the paper it came from. Those studies were peer reviewed. This summary of them was not. Dr. Sarah Luebker is reviewing these pages one at a time and has not reached this one yet, so it carries no medical review date and nothing here is her opinion or her advice to you. Each page gets updated as she reaches it. It is here in the meantime because the science is worth having in one organized place that is easy to find and easy to read. Talk to your own clinician before acting on any of it.