Krill OilFat

• Blood lipidsLikely helps

  This is the one area with consistent meta-analytic support. A systematic review of 7 randomized trials in healthy, dyslipidemic and diabetic adults found krill oil significantly improved lipid parameters [3].
  
  Two conditions came with it: at least 12 weeks of use before triglycerides, total cholesterol and LDL moved, and at least 2 g/day before HDL did [3].
  
  A separate 2023 meta-analysis agreed, reporting significantly lower total cholesterol, LDL and triglycerides, with no serious adverse events [6]. ^[3]

• Blood pressure, glucose and body compositionNot shown to help

  The same 2023 meta-analysis that found the lipid effect looked at these three and found nothing [6].
  
  Blood pressure, blood glucose and body composition were all unaffected by krill oil supplementation [6]. ^[6]

• Cardiovascular risk beyond lipidsPossibly helps

  Moving lipid numbers is not the same as changing cardiovascular outcomes, and the review literature is clear about the gap.
  
  A 2014 clinical review concluded that despite promising early bioavailability data, krill oil's cardiovascular benefit is not established [4].
  
  Krill oil is not addressed in the major ACC/AHA cholesterol guidelines, and that review says it should not be considered first-line omega-3 therapy for the heart [4]. ^[4]

• Knee osteoarthritis painNot shown to help

  The evidence splits cleanly by trial quality, and the best trial is negative.
  
  Smaller early work looked positive: 300 mg/day for 30 days lowered C-reactive protein, pain, stiffness and functional impairment in 90 people with cardiovascular disease, rheumatoid arthritis or osteoarthritis [3][5]. A 2016 trial of 50 people at 2 g/day for 4 weeks moved only 2 of 25 subjective knee-pain measures [3].
  
  Then the largest and most rigorous trial ran: 262 people across 5 Australian cities, 2 g/day for 24 weeks, in knee osteoarthritis with significant pain and MRI-confirmed effusion-synovitis [5].
  
  It found no significant improvement in knee pain versus placebo, and its authors state the findings do not support krill oil for knee pain in this population [5].
  
  That directly contradicts the earlier preliminary evidence. The larger, longer, better-controlled result is the one to weight. ^[5]

• Dry eye diseasePossibly helps

  One double-blind randomized trial found krill oil — about 945 mg EPA and 510 mg DHA daily — significantly improved the ocular surface disease index at day 90 versus placebo, at p=0.02 [3].
  
  The fish oil arm of the same trial did not reach significance on that measure, despite similar EPA and DHA doses [3].
  
  That hints at something krill-specific, perhaps the astaxanthin or the phospholipid form. It is not mechanistically confirmed, and it is one trial. ^[3]

• Period painPossibly helps

  A small trial in people with dysmenorrhea reported fewer painkillers used and improved self-assessed symptoms with krill oil [3].
  
  Small, self-assessed and unreplicated in the sources reviewed here. Read it as a lead, not a finding. ^[3]

• Memory and moodPossibly helps

  Two trials, neither of them encouraging. A 12-week trial in 45 people found no effect on EPA blood concentration, with only a suggestive EEG-based working-memory signal in a sample far too small to conclude from [3].
  
  A year-long trial in 267 adolescents with low omega-3 status found no predictive association between krill oil and neurocognitive test scores [3]. ^[3]

• There is no krill oil deficiency. Krill oil is one source of EPA and DHA, so what follows is essential fatty acid deficiency, per NIH's Office of Dietary Supplements.
• Rough, scaly skin and dermatitis — the recognised signs of essential fatty acid deficiency, whether omega-3 or omega-6.
• Falling plasma and tissue DHA concentrations. No cut-off has been established below which visual, neural or immune function is known to be impaired.
• Almost never seen in practice. NIH ODS calls classical essential fatty acid deficiency in healthy people in the US virtually nonexistent.
• Where it does appear, it is in patients on parenteral nutrition lacking PUFAs — largely resolved since modern feeding formulas carry adequate PUFA levels.
• Sources disagree at the softer end.
  
  Healthline additionally lists dry or irritated skin, hair thinning and joint stiffness as signs of low omega-3 status, and calls that research preliminary [8]. NIH ODS does not recognise those as deficiency signs.^[2]

• Krill oilLower daily doses. A 2024 network meta-analysis found superior omega-3 absorption versus fish oil below 2,000 mg — thou…

  Elemental content

  About 40% phospholipids, mainly phosphatidylcholine; a typical 500 mg capsule holds 60 mg EPA and 30 mg DHA

  Absorption

  Several small crossover studies found the phospholipid form matched or beat re-esterified triglyceride and ethyl-ester fish oil into plasma phospholipids, often without reaching significance

  Best for

  Lower daily doses. A 2024 network meta-analysis found superior omega-3 absorption versus fish oil below 2,000 mg [12] — though WebMD notes other research finds no absorption difference at all [1]

• Fish oil, for comparisonReaching a high absolute EPA+DHA intake without swallowing a handful of capsules — fish oil carries far more per gram

  Elemental content

  Omega-3s as triglycerides, or as ethyl esters in concentrated pharmaceutical products

  Absorption

  Above 2,000–2,900 mg, fish oil ethyl esters may shorten time-to-peak concentration more effectively than krill oil does

  Best for

  Reaching a high absolute EPA+DHA intake without swallowing a handful of capsules — fish oil carries far more per gram [1]

• Astaxanthin contentNothing you can count on yet. It is unclear whether krill oil raises body levels of astaxanthin or those vitamins meani…

  Elemental content

  About 61 mcg per 500 mg krill oil capsule, plus small amounts of vitamin A and vitamin E

  Absorption

  Not established. WebMD notes the amounts are small and vary by product

  Best for

  Nothing you can count on yet. It is unclear whether krill oil raises body levels of astaxanthin or those vitamins meaningfully [1]

• Digestive effects

  The common side effects are mild and gastrointestinal: bad taste or bad breath, heartburn, nausea, upset stomach, diarrhoea, and body odour [1].
  
  Taking it with a fat-containing meal is the usual suggestion for reducing them [9]. ^[1]

• Shellfish and crustacean allergy

  Krill are crustaceans, and a clinical drug monograph lists allergy to other crustaceans or shellfish as a contraindication to krill oil [3].
  
  WebMD advises anyone allergic or possibly allergic to shrimp, crab, lobster, oysters or scallops to raise it with a provider first, since severe reactions are possible [1][11].
  
  Signs needing immediate medical help: breathing problems, swelling of the face, lips, tongue or throat, hives, and dizziness [1]. ^[3]

• Surgery

  WebMD's supplement guide advises stopping krill oil at least two weeks before surgery, because it can slow blood clotting [11]. ^[11]

• Pregnancy and breastfeeding

  Data on krill oil specifically in pregnancy and lactation is described as lacking in the Drugs.com clinical monograph [3].
  
  That monograph points instead to the broader omega-3 evidence base, which is not the same product.
  
  WebMD notes it is not known whether krill oil could affect a pregnancy or harm a fetus, and that many of its nutrients do pass into breast milk [1]. ^[3]

• Anticoagulants and antiplatelets

  Omega-3s including krill oil's may have a mild antiplatelet effect at high doses. Drugs.com advises caution alongside warfarin, aspirin, clopidogrel or prasugrel [3].
  
  NIH ODS adds nuance the blanket warnings lose. The IOM noted 2–15 g/day of EPA and/or DHA might increase bleeding time by reducing platelet aggregation [2].
  
  But most research at 3–6 g/day of fish oil found no significant effect on INR in people taking warfarin [2]. A 2014 review concluded omega-3s do not meaningfully change the risk of clinically significant bleeding [2].
  
  FDA-approved omega-3 package inserts report no clinically significant bleeding episodes in trials, while still advising periodic INR monitoring [2].
  
  So the caution language runs ahead of the trial evidence. Individual variability is a fair reason to keep the caution anyway. ^[3]

• Other supplements affecting bleeding

  The same guide advises caution combining krill oil with ginkgo biloba, garlic or ginger, which may also affect bleeding [11].
  
  It also flags weight-loss medicines that affect fat absorption, since krill oil is an oil [11]. ^[11]

Krill oil is itself the food source, so this section covers the other ways people get the same fatty acids [2].

Cold-water fatty fish are the richest direct sources of EPA and DHA, per NIH's Office of Dietary Supplements. Cooked Atlantic farmed salmon gives about 1.24 g DHA and 0.59 g EPA per 3-ounce serving [2].

Wild Atlantic salmon gives about 1.22 g DHA and 0.35 g EPA per 3 ounces; Atlantic herring about 0.94 g DHA and 0.77 g EPA [2].

Leaner fish — bass, tilapia, cod — and shellfish carry less. Farmed fish usually, though not always, carry more EPA and DHA than wild-caught, depending on feed [2].

Plant foods contain no EPA or DHA at all. They supply the precursor ALA, which the body converts at a reported rate under 15% [2].

The richest ALA sources: flaxseed oil at about 7.26 g per tablespoon, chia seeds at 5.06 g per ounce, English walnuts at 2.57 g per ounce, and canola oil at 1.28 g per tablespoon [2].

Because that conversion is so limited, NIH ODS calls eating EPA and DHA directly — from fish, or from fish, krill or algal oil — the only practical way to raise body levels meaningfully [2].

Some fortified eggs, yogurts, juices, milks and soy beverages are also enriched with DHA [2].

No clinical or government source reviewed here identifies an optimal time of day for krill oil specifically [14][9].

The consistent theme is that consistency beats clock time. EPA and DHA build up gradually in body tissues rather than acting immediately, so daily use matters more than the hour [14].

Healthline's krill oil Q&A recommends taking it with a meal or snack containing some dietary fat, which it says can increase DHA and EPA absorption [9].

That follows the general fat-solubility logic used for fish oil, where dietary fat also tends to reduce reflux and fishy aftertaste. It is generalised omega-3 guidance, not a krill oil trial.

No source found here reports a study comparing morning against evening dosing of krill oil itself [9].