Omega-3s and CKD: What a Landmark Dialysis Trial Tells Us

A CKD diagnosis can feel overwhelming, and many people’s minds jump straight to dialysis. The good news is that for most people diagnosed later in life, kidney failure is unlikely. Research in older adults with CKD shows that most never progress to dialysis.

That doesn’t mean a CKD diagnosis requires no action. What surprises many people is how closely CKD is tied to heart disease. Cardiovascular risk climbs as kidney function declines. In a study of more than one million adults published in the New England Journal of Medicine, people with stage 3a CKD had about a 40% higher risk of cardiovascular events than people with normal kidney function. By stage 3b, that risk roughly doubled. The heart, brain, and kidneys all depend on a healthy vascular system, so protecting it should be one of your main goals.

In November 2025, a trial of omega-3 fats in dialysis patients had nephrologists talking at the American Society of Nephrology’s Kidney Week. As a dietitian, I’ll admit it gives me special pleasure to see doctors excited about a nutrition intervention!

The PISCES Study

Researchers followed 1,228 adults on hemodialysis at 26 sites in Canada and Australia for 3.5 years. Half took 4 grams of high-purity fish oil daily (1.6 g EPA and 0.8 g DHA). The other half took a corn oil placebo.

The fish oil group had a 43% lower rate of serious cardiovascular events, including heart attacks, strokes, cardiac deaths, and vascular-related amputations. Side effects were similar in both groups.

Why I Don’t Think We Should Wait Until Dialysis

For most people with CKD, the bigger threat isn’t kidney failure; it’s the heart. Heart and blood vessel disease is far more likely than ever needing dialysis. That balance shifts in later stages, in younger people, and with certain types of CKD, but the heart still deserves attention at every stage.

PISCES studied people on dialysis, whose heart risk is driven partly by factors specific to dialysis, like fluid and electrolyte shifts and a higher risk of dangerous heart rhythms. Omega-3s may work especially well against that kind of risk. We can’t assume the same 43% benefit applies in earlier stages. One large heart trial, REDUCE-IT, found that a prescription EPA medication reduced heart events across all levels of kidney function, but that was in a specific high-risk population. No trial has been designed to test whether omega-3s prevent heart attacks, strokes, or cardiac deaths in people in earlier stages of CKD. I hope PISCES prompts one!

What we can say is this: low omega-3 levels are common on dialysis, and small studies that measured levels before and after dialysis sessions found that the treatment itself doesn’t remove them. Low levels have also been found in people with CKD who aren’t on dialysis. In one trial, participants started with an average Omega-3 Index of just 3.1%. That suggests the shortfall develops earlier.

The most likely reason is diet. Most Americans already eat less seafood than recommended, and many people cut back further after a CKD diagnosis out of concern about protein, potassium, or phosphorus. Other factors may also play a role. CKD increases oxidative stress and inflammation, which may use up omega-3s faster. Converting plant omega-3s (from flax, chia, and walnuts) into the EPA and DHA your body uses is already inefficient, and researchers suspect CKD may impair it further. Much of this is still being studied, but together it suggests people with CKD may need a more direct source of EPA and DHA.

So my goal isn’t to give everyone with CKD the PISCES dose. It’s to find out whether your levels are low, and if they are, to correct them before years of shortfall add up. Fish is the foundation, but for many people with CKD, a supplement will be needed to close the gap.

How Omega-3s Help the Heart and Beyond

Omega-3s have well-documented effects on heart risk factors and more, several of them especially relevant to CKD:

• Lower triglycerides. This is the most consistent effect of omega-3s, and high triglycerides are common in CKD.
• Modestly lower blood pressure and heart rate. In a trial of people with stage 3–4 CKD, a high dose of omega-3s (4 g/day) lowered 24-hour blood pressure by about 3 points and heart rate by about 4 beats per minute.
• Healthier arteries.Healthier arteries. In a trial of people with CKD not on dialysis whose Omega-3 Index started around 3%, high-dose omega-3s slowed the rise in arterial stiffness and lowered triglycerides.
• Support for mood. Depression is common in CKD. In trials of people with depression, omega-3 supplements modestly improved symptoms when added to standard care. The formulas that helped contained mostly EPA, at about 1 to 2 grams of EPA a day. Omega-3s are not a replacement for depression treatment.
• Relief from itching. Small trials, mostly in people on dialysis, suggest omega-3s may ease the chronic itching that often comes with advanced kidney disease.
• The biggest gains may go to people who eat little fish. In VITAL, a trial of more than 25,000 adults, a daily omega-3 supplement didn’t significantly reduce the main combined outcome of heart attack, stroke, and cardiovascular death, though it did lower heart attacks. The benefit was strongest in people who ate little fish, which suggests omega-3s matter most when intake is low.

How to Test Your Omega-3 Status

The Omega-3 Index measures EPA and DHA as a percentage of the fatty acids in your red blood cell membranes. It reflects roughly the past three to four months of intake. OmegaQuant’s basic test is a validated at-home finger-stick kit that costs about $55 (link below).

An index of 8% or higher is considered desirable; below 4% is considered low. The average American sits at about 4%, and more than half fall below it. Higher levels are linked to lower cardiovascular risk, though no study has tested exactly how high is high enough. Given the elevated heart risk that comes with CKD, I think 8% is a reasonable target.

Testing tells us whether you need a supplement at all and roughly how much. It also lets us retest in a few months to confirm the plan is working.

How to Safely Increase Your Omega-3s

1. Start with food

• Aim for a minimum of two servings of fatty fish per week (about 3 oz cooked each), swapped in for other meats so your total protein stays on target.
• Choose low-mercury options: salmon, sardines, Atlantic mackerel (not king mackerel, which is high in mercury), trout, or herring. Skip pickled, smoked, or breaded fish, which tend to be high in sodium.
• Canned and frozen fish: choose low-sodium or no-salt-added. Skip products listing “sodium tripolyphosphate” or other added phosphates.
• Plant sources are a bonus, not a replacement. Chia, flax, and walnuts are nourishing foods, but your body converts very little of their omega-3 into EPA and DHA. If you eat mostly plant-based, an algae oil supplement can fill the gap (see below).

2. If you choose to supplement

• Get clearance first. Have your nephrologist or primary care physician sign off before starting, especially if you take blood thinners, have upcoming surgery, or have a history of atrial fibrillation (an irregular heart rhythm). In large heart-health trials, omega-3 supplements were linked to a modestly higher risk of atrial fibrillation, mainly at doses above 1 gram per day, and people with reduced kidney function may be more susceptible.
• Work with a renal dietitian on your dose. Your dose depends on your Omega-3 Index, fish intake, labs, and medications. Even people who eat fatty fish twice a week often fall short of 8%, which is another reason testing is useful: your result shows whether food alone is getting you there. For those with a low index, doses commonly used to raise levels fall between 1,000 and 2,000 mg of combined EPA and DHA per day.
• Read the label for EPA + DHA. A “1,000 mg fish oil” capsule may contain far less than 1,000 mg of EPA and DHA. Check the breakdown on the back.
• Quality matters. Supplements aren’t FDA-approved before sale, and independent testing has repeatedly found that EPA and DHA content doesn’t always match the label. Some products also exceed recommended limits for oxidation (rancidity). Skip any capsules that smell strongly fishy or rancid. The brands in my Fullscript storefront (linked below) are ones I’ve vetted for quality.
• Avoid cod liver oil. Its high vitamin A content can build to toxic levels when kidney function is reduced.
• Vegan option: algae oil provides EPA and DHA, though usually in lower amounts and weighted toward DHA, so you may need more capsules to reach a therapeutic dose.
• About prescription omega-3s: Two prescription forms exist. Lovaza (and generics) contains both EPA and DHA. Vascepa (and generics) contains EPA only and is approved to reduce heart events in certain high-risk people already taking a statin. Both are prescribed at 4 grams a day, which provides more EPA and DHA than PISCES used. Prescription products are FDA-regulated for purity and dose, and insurance may cover them if you qualify, usually based on your triglycerides. If your doctor thinks you need a higher dose, ask whether a prescription option makes sense.

Questions? Leave a comment below.

Resources

• Omega-3 Index test: https://omegaquant.com/omega-3-index-basic/ref/1059/
• Supplements: My recommended brands are on my Fullscript storefront, https://us.fullscript.com/s/awhelan/shop/collections/Q29sbGVjdGlvbi0zNTUzMTc=. These are brands I trust for quality and that my clients tolerate well. New orders get 15% off.

Disclosure: I’m an affiliate of OmegaQuant and receive compensation for purchases made through both links above.

References

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