Krill Oil Side Effects: Some (Surprising) Side Effects of Krill Oil

Most health-related supplements are beneficial to health, but most also come with a serving of side effects too. Nothing in life is ever simple! The same can be said for krill oil, a relatively new-comer on the supplement block. In this chat, we’ll discuss krill oil side effects, some of which you might not even think exist!

Before we get into krill oil side effects and potential warnings, we really need to cover what krill oil is. If you’ve ever considered taking fish oil before, or perhaps you already do take it, then krill oil is marketed as a good alternative choice for those rather fishy tasting capsules.

The reason is that it is a good source of omega 3 fatty acids, which is the same reason why we consume fish oil capsules. The difference is that whilst fish oil comes from oily fish (e.g. mackerel and salmon, to name just two), krill oil comes from a crustacean, therefore meaning there’s none of that fishy after-taste to contend with.

A bonus, you’ll surely agree!

But there’s more. Lets explore a little further.

What is Krill Oil, And How is it Different to Fish Oil?

Krill oil is, as we just mentioned, derived from a crustacean called krill. Krill is the food of choice of many marine mammals, including whales and seals. In fact, in Norwegian, ‘krill’ means ‘whale food’. You don’t have to worry about stealing food from whales however, as krill is very plentiful, and therefore a sustainable option for supplements.

The fact that krill isn’t a fish and doesn’t come from a fish means there is no fishy taste, as we just mentioned, but it also means that the capsules are smaller. This means they’re easier to swallow, and that’s a major plus point for anyone who has struggled in the past to take a fish oil capsule, and then found it ‘repeating back’ on them for a short time afterwards. This phenomena is more common than you might think, and has actually put people off taking fish oil capsules in the past.

The thing is, if you don’t eat a lot of fish in your diet and you don’t take a supplement, you’re really missing out on omega 3 nutrients. These are vital for our overall health and wellbeing, including our heart health, brain function, and also in terms of helping reduce the amount of inflammation in our bodies. Anyone with joint pain or arthritis could benefit from taking regular fish oil or krill oil supplements, and studies have shown a marked reduction in symptoms and pain related to this.

Possible Krill Oil Side Effects

Before you start taking any type of supplement you should always consult with your doctor first. Yes, these are beneficial to your health, but certain supplements do interact with conditions and medications, and you need to be sure that you’re not falling into any of those categories. Just a quick chat should be enough to reassure you in either direction.

Krill oil side effects are actually very similar to the side effects of regular, traditional fish oil capsules. The only real difference is that with krill oil, you’re probably not going to get the fishy after-taste that you might with fish oil capsules. As we mentioned, this is because krill isn’t a fish, it’s a crustacean.

The most common side effects of krill oil are:

  • Stomach upsets, e.g. diarrhoea
  • Stomach ache
  • Change in appetite, usually loss of appetite
  • Nausea
  • Bloating
  • Gas
  • Change in the way things taste

These are not extremely common, but they have been reported to be linked to krill oil and are amongst the side effects which most people do report, if they are to have any adverse effects.

Of course, there is the possibility that you may be allergic to an ingredient, and in that case, a severe reaction will occur. If that happens, stop the supplements immediately and seek urgent help.

Symptoms of a reaction include difficulty breathing, swelling of your tongue, face, lips, or throat, hives, an irregular heartbeat, chest pain, flu-like symptoms, fever or chills, and aching body. Again, seek out urgent help if you notice these symptoms, and stop the supplements straightaway.

Can Everyone Take Krill Oil?


We mentioned about checking things out with your doctor and that is the most pertinent advice to give. There are certain conditions and medications which interact with krill oil, however there hasn’t been enough research into why this is and to what extent.

Whilst we know that krill oil is beneficial, we don’t know the exact amount and severity of krill oil side effects, we don’t know the actual standard, across the body dosage, and as a result, that means it goes on a case by case basis. Your doctor is the only one to give you the answers.

Overall however, there are some situations which krill oil shouldn’t be used, or should be used in extreme caution (again, after speaking to your doctor).

Anyone With a Fish, Shrimp, or General Seafood/Shellfish Allergy

Not enough research has gone into whether krill oil supplements are suitable for those who have a shellfish or general seafood allergy. Again, it completely depends upon your allergy severity and whether it was a one off case or not. Speak to your doctor about this, but don’t take any risks, because if a reaction occurs, it could be severe.

Anyone Who is Taking Blood Thinning Medications

Krill oil could affect blood clotting within the body, and slow down the clotting process, although there is no strong evidence of this. If you are taking any medications to thin the blood, you should speak to your doctor before you think about taking krill oil supplements.

Anyone Who is About to Have Surgery in The Near Future

If you are having a planned operation in the near future, you should stop taking your krill oil at least two weeks beforehand. For the exact timescale, again, speak to your doctor. This is because of the reason we just mentioned, that krill oil may slow down blood clotting time.

Anyone With Diabetes

There is a suggestion that krill oil could lower blood sugar in patients suffering with diabetes. This means blood sugar needs to be monitored very carefully, but even before you consider taking these supplements, you know what to do – speak to your doctor. Studies have suggested caution should be taken.

Anyone Who is Obese

There is a suggestion that krill oil can affect the effectiveness of insulin in anyone who is overweight or obese. This could increase the overall risk of suffering from diabetes or heart problems in the future, especially in developing heart disease.

Anyone Who is Pregnant or Breastfeeding

There isn’t enough research to firmly confirm or deny whether krill oil is harmful in pregnancy and breastfeeding or not. If you are thinking about using krill oil and you’re considering pregnancy, speak to your doctor first. Similarly, follow the same advice if you’re currently pregnant or breastfeeding.

Anyone Who Has Blood Pressure Issues

As a very rare side effects of krill oil, the supplements could affect blood pressure. For that reason, if you have any issues with blood pressure, whether you’re on medications or not, it’s vital you speak to your doctor first.

How to Find The Best Krill Oil Product

There are countless krill oil products on the market, but this is a market which doesn’t really have the greatest amount of regulation. This means you could spend a good amount of money on a product that has little benefit to you.

Each product will also have its own serving amount (dosage), and these will vary from choice to choice. For that reason, always read the label and follow instructions on the bottle in terms of how to take the supplements, how many to take, and when to take them. If you’re not sure, again, speak to your doctor.

The downside of krill oil versus fish oil is that krill oil is generally more expensive. This isn’t a huge amount, but the difference is still there, and over time that could add up to a good amount of money. The reason for this is that krill oil is harder to harvest than fish oil, and the overall process is more complicated.

You’re also getting an added bonus when you choose krill oil, because it contains a powerful antioxidant, called astaxanthin. Basically that means you’re getting the specific benefits of omega 3s, but you’re also getting a quality antioxidant within the same dose. Again, dosages of astaxanthin vary between products, with some having more content than others. This is another reason why you should shop around.

The most important things to look for are:

  • Amount of pure krill oil within the product (note the word ‘pure’, as this means it is completed natural)
  • The amount of EPA and DHA (omega 3s)
  • The amount of astaxanthin within the product
  • The serving amount, is it two or one?
  • The amount of servings in each bottle
  • Whether the capsule has a flavouring, to make it taste better and therefore easier to swallow
  • The type of capsule, e.g. some are soft ‘gums’, although you should never chew a krill oil supplement and you should always swallow it whole
  • Reviews – Read previous reviews and make sure they’re positive
  • Price

How to Take Krill Oil

How to take each product will vary according to the instructions on the bottle, so again, read the label and follow what it tells you to do. Overall, krill oil supplements are kept in much the same way as fish oil supplements, e.g. at room temperature and out of direct sunlight.

You should never puncture a krill oil capsule, and you should always simply swallow it whole. The type of supplement might say it is a ‘soft gum’, or other wording, but that doesn’t mean you can chew it – never chew a krill oil supplements. The wording of this basically means that it is easy to swallow because it isn’t hard. You can choose to swallow both together (if the serving is more than one), or one at a time. Just read the label for exact advice.

Do The Benefits of Krill Oil Outweigh The Side Effects?

On the whole, that is something that only you and your doctor can decide. Taking krill oil is a fantastic way to get a good, daily dose of omega 3 fatty acids. We can’t deny that fact, and doctors have been advising us for years to take fish oil, especially if our general diet is lacking fish intake.

The benefits of omega 3s are huge, and these are actually vital for health and wellbeing in general. If you don’t get them in any guise, you’re going to be lacking in health, possibly quite seriously.

For that reason, supplements are a good idea, but you should always proceed with caution if you have any other conditions, or if you’re taking any medications. We do not have an exhaustive list of the medications which may or may not interact with krill oil, because not enough research has gone into this. For that reason, your doctor is the only person who can advise.

Overall however, krill oil should be suitable for the vast majority of people, and this means you can gain the benefits of omega 3s, without the rather unpleasant fishy after-taste that works hand in hand for many people taking regular fish oil capsules.

The side effects of krill oil are also very similar to those of fish oil supplements, which have been on the market for years. You shouldn’t experience a host of unpleasant effects from taking krill oil, and if you do, it could be that it simply isn’t suitable for you.

Weighing up the benefits versus the possible effects is something we need to do with everything related to our health, and whilst more research needs to go into the actual side effects of krill oil, for the time being, they seem quite minimal.

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