Krill oil has been making quiet but steady waves in the world of nutrition. It’s not as famous as fish oil, but those who swear by it say it’s more than just another omega-3 supplement.
Sourced from tiny Antarctic crustaceans called Euphausia superba, krill oil brings together the well-known benefits of omega-3 fatty acids with unique compounds you won’t find in most fish oils. But — and this is important — it’s not without its potential downsides.
In this guide, we’ll explore the latest 2025 research, real benefits, possible side effects and contraindications, how to take it effectively, and whether it’s truly worth choosing over fish oil.
What is Krill Oil?
Krill are small, shrimp-like crustaceans found in the cold waters of the Antarctic Ocean. They’re a major food source for whales, seals, penguins, and other marine life — and now, through sustainable harvesting, for humans in supplement form.
What sets krill oil apart from fish oil:
- Omega-3 structure: In krill oil, omega-3s are bound to phospholipids instead of triglycerides, which may make them easier to absorb.
- Astaxanthin: A reddish antioxidant pigment that helps protect the oil from oxidation and may add its own health benefits.
- Choline: A nutrient important for brain and liver health.
Benefits of Krill Oil
1. Heart Health & Cholesterol
Heart protection is the number one reason people turn to omega-3 supplements. Krill oil has shown promise in:
- Lowering triglycerides
- Reducing LDL (“bad”) cholesterol
- Increasing HDL (“good”) cholesterol
A 2023 meta-analysis found that krill oil supplementation improved several lipid profile markers, though effects on blood pressure and overall cardiovascular risk still need further research.
2. Preserving Muscle During Weight Loss
One of the most exciting findings comes from a July 2025 randomized trial.
Researchers tested krill oil in adults doing alternate-day fasting and found:
- No muscle mass loss compared to placebo (placebo group lost both muscle and grip strength)
- Lower inflammation markers like TNF-α
- A drop in systolic blood pressure
- Higher blood EPA, DHA, and omega-3 index
For anyone aiming to lose weight without sacrificing strength, these results are noteworthy.
3. Joint Pain Relief in Osteoarthritis
A 2025 meta-analysis of five clinical trials with 730 participants found that krill oil significantly:
- Reduced knee pain
- Eased morning stiffness
- Improved joint function
It was also well tolerated, with no increase in serious adverse events. This makes it a promising natural option for those managing osteoarthritis symptoms.
4. Mental Wellbeing and Mood
Omega-3s, including those in krill oil, play a role in brain health and mood regulation.
A 2025 comparative study found that both krill oil and fish oil improved symptoms of depression, anxiety, and stress. While not a replacement for professional mental health care, it could offer an additional supportive effect.
5. Anti-Inflammatory and Antioxidant Support
Between its omega-3 fatty acids and astaxanthin content, krill oil has strong anti-inflammatory potential. Lowering inflammation can contribute to:
- Better heart and joint health
- Reduced oxidative stress
- Improved exercise recovery
Side Effects of Krill Oil
Krill oil is generally considered safe for most healthy adults, but like any supplement, it can have side effects — and knowing them helps you decide if it’s right for you.
Below, we break them down into common, less common but serious, and specific contraindications.
1. Common Side Effects
These tend to be mild and often go away as your body adjusts, especially if you take krill oil with food:
- Digestive discomfort — bloating, mild cramping, loose stools, or diarrhea are the most reported issues. This is usually due to the fat content of the oil.
- Fishy aftertaste or “burps” — less common with krill oil than fish oil, thanks to astaxanthin, but still possible.
- Heartburn or indigestion — especially if taken on an empty stomach.
- Mild headaches — can occur in sensitive individuals, typically resolving after the first week.
Tip: Starting with a lower dose and increasing gradually can reduce the likelihood of these effects.
2. Less Common but More Serious Side Effects
These are rare but important to be aware of:
- Increased bleeding risk
Omega-3 fatty acids, including those in krill oil, can thin the blood and may increase bleeding time.
This is particularly important if you:- Take anticoagulants (like warfarin, apixaban, or aspirin)
- Have a diagnosed bleeding disorder
- Are scheduled for surgery (stop krill oil at least 2 weeks beforehand)
- Allergic reactions
Krill are shellfish. If you have a shellfish allergy, krill oil is not safe — even trace exposure could cause a reaction ranging from mild itching to severe anaphylaxis. - Changes in blood sugar
Some studies suggest omega-3s can slightly affect glucose metabolism, so diabetics or pre-diabetics should monitor their levels more closely when starting supplementation.
3. Contraindications — Who Should Avoid Krill Oil
Krill oil is not recommended for:
- People with shellfish allergies
- Those on blood-thinning medications unless approved by a doctor
- Individuals with bleeding disorders
- Pregnant or breastfeeding women without medical clearance
- People undergoing surgery soon
4. How to Reduce the Risk of Side Effects
- Take with meals — particularly meals containing healthy fats, to improve absorption and reduce stomach upset.
- Check the dose — more isn’t always better. For most, 300 mg–1 g per day (combined EPA+DHA) is enough.
- Buy from reputable brands — look for third-party testing to ensure purity and avoid contaminants.
- Start slow — especially if you’ve never taken omega-3 supplements before.
Bottom line:
Most side effects of krill oil are mild and temporary, but the potential for serious interactions — particularly with blood thinners and allergies — means you should always check with a healthcare provider before starting.
Krill Oil vs Fish Oil
| Feature | Krill Oil | Fish Oil |
|---|---|---|
| Omega-3 Form | Phospholipids (may absorb better) | Triglycerides or ethyl esters |
| Antioxidants | Contains astaxanthin | Typically none |
| Choline | Present | Absent |
| Taste / Aftertaste | Less fishy for many users | More common fishy burps |
| Cost | 3–4× more expensive | More affordable |
| Research Base | Growing but smaller | Extensive, decades of data |
How to Take Krill Oil
- Dosage: Commonly 300 mg – 1 g daily (check EPA+DHA content, not just total oil)
- Best time: With a meal containing healthy fats for better absorption
- Forms: Softgels are most popular; liquids and gummies exist but may have lower potency
Sustainability Considerations
Krill are the foundation of the Antarctic food web, feeding whales, penguins, and seals. Overharvesting can disrupt this balance. Look for brands with MSC (Marine Stewardship Council) certification to ensure sustainable sourcing.
Related Reads on MasalaMonk
- How Omega-3 Fatty Acids Help Fight Chronic Inflammation
- Unpacking the Health Benefits of Oily Fish
- Fish Oil and Cortisol: Can Omega-3 Help Manage Stress Hormones?
- Vegan Omega-3 Snack Ideas for Pregnant Women
Final Thoughts
Krill oil offers a unique package of omega-3s, antioxidants, and choline that may support heart, joint, brain, and muscle health. The latest studies even suggest it can help maintain muscle during weight loss and ease arthritis pain.
That said, it’s not for everyone. People with shellfish allergies, bleeding risks, or certain medical conditions should steer clear — and as with any supplement, it works best as part of an overall healthy lifestyle, not as a replacement for one.
If you decide to try krill oil, choose a sustainable, high-quality brand, start with a moderate dose, and see how your body responds.
Krill Oil FAQs
1. What is krill oil used for?
Krill oil is mainly taken as an omega-3 supplement to support heart health, reduce inflammation, improve joint comfort, and maintain brain function. Recent studies also suggest it may help preserve muscle during weight loss and improve mood.
2. What are the side effects of krill oil?
Common side effects include mild digestive upset, fishy aftertaste, heartburn, and occasional headaches. Less common risks include increased bleeding tendency, allergic reactions in those with shellfish allergies, and possible changes in blood sugar.
3. Who should not take krill oil?
Avoid krill oil if you have a shellfish allergy, a bleeding disorder, are taking blood-thinning medication, are scheduled for surgery, or are pregnant or breastfeeding without medical approval.
4. Is krill oil better than fish oil?
Krill oil may have better absorption due to phospholipid-bound omega-3s and contains astaxanthin and choline, which fish oil lacks. However, fish oil is more affordable, widely studied, and provides higher total omega-3 content per dose.
5. How much krill oil should I take daily?
Most studies use 300 mg to 1 g daily, focusing on total EPA+DHA content rather than the overall oil weight. Always follow your supplement label and consult a healthcare professional for personalized advice.
6. Can krill oil cause bleeding?
Yes. Like other omega-3 supplements, krill oil can thin the blood and may increase bleeding risk, especially when combined with anticoagulant or antiplatelet medications. Consult your doctor before use.
7. Can I take krill oil if I’m pregnant?
Krill oil is a source of omega-3s important for pregnancy, but safety data is limited. Consult your doctor before using it during pregnancy or while breastfeeding.
8. How long does it take for krill oil to work?
Benefits like improved omega-3 blood levels can appear in a few weeks, but noticeable changes in joint comfort, mood, or cholesterol may take 8–12 weeks of consistent use.
9. Is krill oil safe for diabetics?
It may be safe for many diabetics, but omega-3s can influence blood sugar regulation in some people. Monitor your glucose levels and consult your healthcare provider before starting.
10. How do I choose a good krill oil supplement?
Look for MSC-certified sustainable sourcing, third-party purity testing, and clear labeling of EPA and DHA content. Avoid supplements with unnecessary fillers or artificial colors.
