Why Do I Feel Sick After Taking Omega-3? Causes and Solutions for Digestive Distress

December 18, 2025 •

4 min read

According to the NIH, mild side effects like nausea and stomach discomfort are among the most common complaints reported by people taking omega-3 supplements. If you're wondering "why do I feel sick after taking omega-3," understanding the root cause is the first step toward finding relief.

Quick Summary

Digestive distress such as nausea, burping, and stomach upset can occur after consuming omega-3 supplements. The culprits often include high doses, rancidity, and improper timing or form. Simple adjustments to your routine can help mitigate these issues effectively.

Key Points

High Dosage Is a Common Culprit: Excessive omega-3 can trigger nausea and bloating; consider reducing your dose, especially if it exceeds 3g daily.
Rancidity Causes Fishy Burps: If your supplement has a strong, unpleasant smell, it may be oxidized, leading to fishy reflux; opt for high-quality, third-party tested brands.
Timing Matters for Digestion: Taking omega-3 with a meal, particularly one containing fat, significantly improves absorption and reduces digestive upset.
Try Enteric-Coated or Alternative Sources: To combat fishy burps, consider enteric-coated capsules that dissolve in the intestine or switch to algae oil, a vegan alternative.
Start Low, Go Slow: If you're new to supplements, begin with a lower dose and gradually increase it as your body adapts to minimize initial side effects.
Consult a Professional for Persistent Issues: If symptoms are severe or don't improve with adjustments, speak with a doctor to rule out an allergy or other health concerns.

Common Reasons for Feeling Sick After Taking Omega-3

Digestive issues are the most frequently reported side effects associated with omega-3 supplementation. These symptoms can range from mild discomfort to more pronounced nausea and stomach upset. Understanding the potential causes can help you pinpoint the problem and find the right solution.

High Dosage

Taking an excessively high dose of omega-3 is a primary reason for gastrointestinal distress. The American Heart Association considers up to 3 grams of fish oil per day safe for most people, but exceeding this can increase the risk of side effects. The high fat content in concentrated supplements can overwhelm the digestive system, leading to feelings of nausea, bloating, and loose stools. Starting with a lower dose and gradually increasing it as your body adjusts can help prevent this issue.

Poor Quality or Rancid Supplements

Unfortunately, not all omega-3 supplements are created equal. If your supplement has a strong, unpleasant fishy smell or aftertaste, it may have gone rancid or is of poor quality. Oxidized (rancid) fish oil is known to cause a range of unpleasant digestive symptoms, including burping and reflux that tastes distinctly of fish. Always check the expiration date and buy from reputable brands that provide proof of third-party testing for purity.

Improper Timing and Absorption

Timing is another crucial factor. Taking your omega-3 supplement on an empty stomach, particularly in the morning, can increase the likelihood of nausea and acid reflux. Because omega-3s are fat-soluble, they are best absorbed when taken with a meal containing other fats. This helps slow down digestion and integrate the fatty acids more smoothly, preventing them from floating to the top of your stomach and causing burps.

Individual Sensitivity

Every individual's body responds differently. Some people may have a more sensitive digestive system and are simply more prone to gastrointestinal side effects from supplements. In rare cases, an individual could have an allergy to fish or shellfish, which could manifest in digestive symptoms. If symptoms are severe or accompanied by other allergic reactions, it is essential to consult a doctor.

Practical Solutions to Prevent Nausea and Upset Stomach

If you're experiencing side effects, don't give up on omega-3 just yet. There are several simple strategies you can try to improve your tolerance and minimize digestive upset.

Take Supplements with Food

This is one of the most effective and easiest solutions. Taking your omega-3 with your largest meal of the day, or one that contains healthy fats, dramatically improves absorption and reduces stomach irritation. A meal with avocado, nuts, or olive oil is an excellent choice. Splitting a high daily dose into two smaller ones, taken with separate meals, can also be beneficial.

Consider Enteric-Coated Capsules

Enteric-coated capsules are designed to bypass the stomach and dissolve in the small intestine. This prevents the contents from being released in the stomach, which is the primary cause of fishy burps and reflux. If this is your main complaint, a switch to an enteric-coated product may be the best solution for you.

Freeze Your Capsules

For some, a simple trick is to freeze their omega-3 capsules. This delays the breakdown of the gelatin shell, allowing the capsule to travel further down the digestive tract before the oil is released. This can significantly reduce the risk of fishy burps and aftertaste.

Switch to a Different Source of Omega-3

If fish oil is consistently causing problems, you might consider an alternative. Algae oil, derived from marine algae, provides a direct source of EPA and DHA without the fishy taste or smell. For those with fish allergies, this is a much safer option. Krill oil is another alternative that is also known to have better absorption and fewer reported fishy burps for some individuals.

A Comparison of Omega-3 Supplement Sources


Feature	Fish Oil	Algae Oil (Vegan)	Krill Oil
Source	Fatty fish like sardines, mackerel, anchovies	Marine microalgae	Krill (small crustaceans)
Key Omega-3s	EPA and DHA	EPA and DHA	EPA and DHA
Bioavailability	Generally good, but absorption can vary	Very good; a direct source	Very good; bound to phospholipids
Common Side Effects	Nausea, fishy burps, upset stomach	Fewer digestive side effects often reported	May reduce fishy aftertaste
Purity Concerns	Can be susceptible to rancidity and contaminants if not from reputable source	Often considered cleaner as they are lower on the food chain	Generally lower risk of contaminants due to small size
Consideration	Most widely available and studied	Excellent option for vegans and those with fish sensitivity	Good alternative for improved absorption and reduced burping

When to Contact a Healthcare Provider

While most omega-3 side effects are mild and easily managed, there are times when it's necessary to consult a healthcare professional. If your symptoms are severe, persistent, or worsen over time, it's wise to speak with a doctor. They can help rule out underlying conditions or allergies and ensure the supplement isn't interacting with other medications you are taking. The NIH provides comprehensive information on potential interactions.

Conclusion

Feeling sick after taking omega-3 is a common but manageable issue, and it doesn't mean you have to abandon the health benefits these fatty acids provide. By adjusting your dosage, taking your supplements with a meal, or switching to an enteric-coated or alternative source like algae oil, you can often find a solution. Prioritizing a high-quality, non-rancid product is also key to a better experience. For most people, a simple adjustment is all that is needed to reap the rewards of omega-3 supplementation without the unpleasant side effects.

Frequently Asked Questions

Yes, omega-3 supplements can cause nausea, along with other digestive issues like burping, bloating, and stomach discomfort, especially if taken in high doses or on an empty stomach.

To prevent feeling sick, try taking your supplement with a meal containing fat, freezing the capsules to delay digestion, or switching to an enteric-coated product that bypasses the stomach.

A strong, persistent fishy burp or aftertaste can be a sign that the omega-3 supplement has oxidized or is of poor quality. High-quality products typically have minimal aftertaste.

The timing is less important than consistency, but taking omega-3 with a meal is key for absorption. Some people find that taking it in the morning or evening with a meal works best for them.

Algae oil is an excellent plant-based alternative that provides both EPA and DHA and is often reported to cause fewer digestive side effects compared to fish oil. Krill oil is another alternative that may have improved absorption.

While rare, an allergic reaction is possible if you are allergic to fish or shellfish, as some fish oil supplements may contain trace proteins. Always consult a doctor if you suspect an allergy.

Yes, taking more than the recommended dosage, typically over 3 grams per day, can increase the risk of side effects like bleeding and worsening digestive issues. Always consult your doctor before exceeding recommended dosages.

If you experience mild symptoms, try adjusting your intake first by changing the timing or dosage. However, if symptoms are severe or persistent, you should stop and consult a healthcare provider.