Krill: Everything You Need to Know
Medically reviewed by Melissa Nieves, LND, RD
Krill are tiny shrimp-like water-living animals, which are sources of krill oil.
Krill oil contains omega-3 fatty acids, primarily eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
In addition to vitamin A and vitamin E, krill is also a source of astaxanthin, a pigment (natural coloring) found in some water-living organisms.
Astaxanthin is also a carotenoid (organic pigments that plants and algae produce) with no vitamin A activity.
These components (parts or ingredients) are likely responsible for how krill oil works.
This article discusses what you should know about krill oil—its health claims, side effects, and interactions.
Explainer
Dietary supplements are not regulated the same way drugs are in the United States, meaning the Food and Drug Administration (FDA) does not approve them for safety and effectiveness before products are marketed. Choose a supplement tested by a trusted third party, such as the U.S. Pharmacopeia (USP), ConsumerLab.com, or NSF, whenever possible.
However, even if supplements are third-party tested, they are not necessarily safe for all or effective in general. Therefore, talking to your healthcare provider about any supplements you plan to take and checking in about potential interactions with other supplements or medications is important.
Supplement Facts
Active Ingredient(s): Omega-3 fatty acids, vitamin A, vitamin E, astaxanthin
Alternate Names(s): Krill oil, omega-3 fatty acids
Legal Status: Food and dietary supplement
Suggested Dose: May vary based on dosage form, age, sex, and medical condition
Safety Considerations: Possible side effects, interactions, and special considerations for children, pregnancy, and breastfeeding
Uses of Krill
Explainer
Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian, pharmacist, or healthcare provider. No supplement is intended to treat, cure, or prevent disease.
While more extensive research is necessary regarding effectiveness, people generally use krill to treat various health conditions.
Research is most robust for the following:
Heart health
Knee pain due to osteoarthritis
Premenstrual period syndrome (PMS)
Heart Health
Some clinical trials have studied the effects of natural products—like krill—on heart disease risk factors, such as high cholesterol and hypertension (high blood pressure).
For example, a systematic review and meta-analysis (a methodical review and analysis of a collection of studies) included several krill oil–related studies that focused on cholesterol effects.
The results showed that krill oil lowered low-density lipoprotein (LDL) cholesterol ("bad cholesterol") and triglycerides (TG).
Additionally, it was shown that krill oil also increased high-density lipoprotein (HDL) cholesterol ("good cholesterol"), but lacked a significant effect on total cholesterol levels.
Per another study, a small clinical trial on the effects of krill powder in people with excess weight and moderately high blood pressure was conducted.
While the risk of side effects was low, krill powder didn't significantly change blood pressure or cholesterol levels.
Overall, because results from both studies were mixed, further extensive research with more people is warranted.
Future clinical trials should also assess if krill's potential effects on cholesterol and blood pressure also translate to positive heart-related outcomes.
Osteoarthritis Knee Pain
In a small six-month study, people with mild to moderate knee pain due to osteoarthritis (wear-and-tear arthritis) were divided into two groups—the krill and placebo groups.
The krill group experienced more knee pain and stiffness relief than the placebo. There was also an improvement in knee physical function, such as walking.
While the study results were positive, further rigorous clinical trials that include a larger group of people are still warranted.
Premenstural Syndrome
A small clinical trial studied the effects of a combination supplement that contains krill oil.
After three months of taking the daily supplement, the study participants experienced relief from several PMS symptoms.
Some of these symptoms include:
Appetite changes
Bloating (gas)
Breast tenderness
Mood changes
Skin reactions
Sleeping problems
Although the results are promising, it isn't easy to quantify the effects of krill oil. This study used a supplement that combined krill oil with other vitamins and natural products.
For this reason, future clinical trials should study krill oil separately to understand krill oil's effects better.
Moreover, future research must include higher-quality, more extensive clinical trials.
What Are the Side Effects of Krill?
Like many medications and natural products, krill supplements may have side effects.
Common Side Effects
Common side effects associated with the consumption of krill supplements may include:
Bloating (gas)
Symptoms similar to the common cold
Headache
Musculoskeletal injuries—like injuries to the muscles and joints
Severe Side Effects
In a small study on krill powder, participants with excess weight and moderately high blood pressure didn't experience severe side effects.
The FDA has placed krill on the GRAS (generally recognized as safe) list.
Still, a severe allergic reaction is a profound side effect possible with any medication or natural product.
If you're having a severe allergic reaction, symptoms may include breathing difficulties, itchiness, and rash.
Additionally, krill is a rich source of omega-3 fatty acids, including eicosapentaenoic acid (EPA, a type of omega-3 fatty acid) and docosahexaenoic acid (DHA, a type of omega-3 fatty acid).
Because of this, high doses of EPA and DHA might result in the following serious side effects:
Greater chance of infection from a lower-functioning immune system (the body's defense system)
Increased risk of bleeding
If you're having a severe allergic reaction or if any of your symptoms feel life-threatening, call 911 and get medical help right away.
Precautions
A healthcare provider may advise against krill if any of the following applies to you:
Severe allergic reaction: Avoid krill if you have a known allergy to it or its ingredients or parts. For example, avoid krill if you have a shellfish allergy.
For clarification on whether it's safe, ask a registered dietitian, pharmacist, or healthcare provider for more information.
Pregnancy: In general, krill is a rich source of omega-3, which is an essential fatty acid that the body cannot make on its own.
Moreover, there are daily adequate intake (AI) amounts of omega-3 fatty acids for everyone, including those who are pregnant. AIs are used when isn't enough evidence for recommended dietary allowances (RDAs) yet. The AI of omega-3 fatty acids for pregnant people is 1.4 grams (g).
Contact a healthcare provider to discuss the benefits, risks, and requirements when pregnant.
Breastfeeding: Krill is a source of omega-3, which is an essential fatty acid. There are AIs of omega-3 fatty acids for breastfeeding parents. The AI of omega-3 fatty acids for breastfeeding parents is 1.3 g.
Reach out to a healthcare provider to discuss the benefits, risks, and requirements when breastfeeding.
Adults over 65: Older adults have participated in some studies on krill, a rich source of omega, an essential fatty acid called omega-3. There are also AIs of omega-3 fatty acids for people older than 50.
For males, the AI is 1.6 g for this age group. And for females, the AI is 1.1 g.
In general, use krill cautiously. Some older adults may have a higher likelihood of side effects from medications.
Children: Krill is rich in omega-3, an essential fatty acid.
There are AIs of omega-3 fatty acids for children of various ages:
Birth to 12 months: 0.5 g
1–3 years: 0.7 g
4–8 years: 0.9 g
But once your child is at least 9 years old, the AIs slightly change depending on your child's sex:
9–13 years: 1.2 g for males and 1 g for females
14–18 years: 1.6 g for males and 1.1 g for females
Talk with a healthcare provider if you're considering krill for your child.
Dosage: How Much Krill Should I Use?
Explainer
Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your individual needs.
Krill is rich in omega-3, an essential fatty acid the body cannot make alone.
AI is an amount of vitamin, mineral, or fatty acid assumed to be enough to meet nutritional needs. These AIs may vary based on age, sex, pregnancy, and breastfeeding status.
However, in clinical trials that studied the potential effects of krill, the dosage forms varied.
In studies with krill oil, the amount of krill oil and specific amounts of the EPA and DHA omega-3 fatty acids also differed.
A clinical trial also combined krill oil with other vitamins and natural products. In general, additional rigorous research with higher-quality, larger studies is warranted
For these reasons, there are no guidelines on the appropriate dosage to take krill supplements for any condition. But for cholesterol effects, many studies used krill in a 500 milligram (mg) capsule form with krill oil dosages varying between 1 g and 3 g per day.
Follow a healthcare provider's recommendations or product label instructions if you take a manganese supplement.
What Happens If I Use Too Much Krill?
Krill is rich in omega-3 fatty acids, primarily EPA and DHA.
At high doses of EPA and DHA, you might experience the following:
Increased risk of infection from a lower-functioning immune system
Increased risk of bleeding
If you suspect you are experiencing life-threatening side effects from too much krill, seek immediate medical attention.
Interactions
Krill might interact with the following medications:
Blood thinners: Krill is a rich source of omega-3 fatty acids. But high doses of the EPA and DHA omega-3 fatty acids may increase your risk of bleeding. Combining krill with blood thinners may increase the risk of severe bruising and bleeding side effects. An example of a blood thinner is Jantoven (warfarin). If you take krill and a blood thinner, healthcare providers may want to monitor you and make any necessary medication adjustments closely.
Cholesterol medications: Krill may affect your cholesterol levels. This may have additive effects with cholesterol medications, such as statins and omega-3 fatty acids.
Immune support medications: High doses of the EPA and DHA omega-3 fatty acids may affect your immune system. For this reason, caution should be used with other medications—like Humira (adalimumab)—that affect the immune system.
It is essential to carefully read a supplement's ingredients list and nutrition facts panel to know which ingredients and how much of each ingredient is included. Please review the supplement label with your healthcare provider to discuss potential interactions with foods, other supplements, and medications.
How to Store Krill
Storage instructions may vary for different products. Carefully read the directions and packaging label on the container.
Generally, most medicines' optimal storage condition is in a cool and dry place. You should also keep your medications tightly closed and out of the reach of children and pets, ideally locked in a cabinet or closet.
Discard after one year or as indicated on the packaging. Avoid putting unused and expired products down the drain or in the toilet. Visit the FDA website to know where and how to discard all unused and expired medications.
You can also find disposal boxes in your area.
Ask a pharmacist or healthcare provider if you have any questions about how to dispose of your medications or natural products.
If you plan to travel with krill, get familiar with your final destination's regulations. The U.S. Embassy & Consulates can be a helpful resource.
Ask a healthcare provider how to travel with your medications or natural products if necessary...
Similar Supplements
Krill may affect high cholesterol for heart health, osteoarthritis, knee pain, and PMS.
Other similar supplements include:
Astaxanthin: Krill oil contains astaxanthin. For this reason, astaxanthin may have similar effects to krill.
Avocado/soybean unsaponifiable (ASU): ASU may help relieve osteoarthritis symptoms. But more safety data is necessary.
Chasteberry: Initial studies suggest that chasteberry might help relieve menstrual period symptoms. But the evidence isn't strong enough to conclude one way or another.
Garlic: Garlic may lower your cholesterol levels.
Omega-3 fatty acids: Krill is a source of omega-3 fatty acids. For this reason, omega-3 fatty acids may have some effects that are similar to krill.
Only combine multiple natural products once you first talk with a healthcare provider, pharmacist, or dietitian. Checking in can help you avoid possible harmful interactions and side effects and ensure you're giving these supplements a fair trial at appropriate doses.
Frequently Asked Questions
What is the most common dosage form of krill?
Krill supplements are available in a few different dosage forms—with capsules being the most common.
Are there krill supplements from manufacturers in the United States?
Yes. Manufacturers in the United States make krill supplements.
How do I take krill safely?
To safely take natural products—like krill—inform your healthcare providers and pharmacists about any medication changes. This includes over-the-counter (OTC), herbal, natural medicines, and supplements.
Your healthcare provider can help prevent possible interactions and side effects. They can also ensure you’re giving krill a fair trial at appropriate doses.
Sources of Krill & What to Look For
There are a few different sources of krill. Health nutrition guidelines typically prioritize food sources to improve the diet. While food sources are preferable, there might still be a place for supplements for certain groups of people, such as those with certain medical conditions.
Food Sources of Krill
Krill is a tiny shrimp-like water-living animal. The U.S. Department of Agriculture (USDA) considers krill a food.
Krill Supplements
Krill supplements are commonly available in capsule form.
Other dosage forms of krill may include:
Food bars
Gummies or soft chewable
K-cup
Liquid
Powder
Tablets
But some of these other forms might also contain other ingredients.
What you decide on will depend on your preference and what you hope to receive regarding health benefits. Each product may work a bit differently, depending on the form.
So, following a healthcare provider's recommendations or label directions is essential.
Summary
Krill is a tiny shrimp-like water-living animal. As a source of omega-3 fatty acids and astaxanthin, krill may have some potential uses in high cholesterol for heart health, osteoarthritis, knee pain, and PMS. Before using krill, get the advice of a registered dietitian, pharmacist, or healthcare provider to help you decide if krill is right for you.
