How to choose a fish oil supplement: skip the front of the bottle and read five details on the label. They are the EPA and DHA per serving, the serving size and daily count, freshness and form, the fish source and allergens, and proof of independent testing. Together they tell you how much omega-3 you are really getting, whether the oil is likely to be in good condition, and whether it suits your diet. Here is what each detail means and what a clear answer looks like, using the Pure Omega+™ label as a worked example.
Key takeaways
- The amount of fish oil is not the amount of omega-3; the EPA and DHA lines are the numbers that count.
- Every figure on a Supplement Facts panel refers to one serving, which may be more than one softgel.
- Fish oil can oxidize, and studies of store-bought products have found many above recommended oxidation limits.
- A fish oil label must declare the fish species as an allergen, and a gelatin softgel is not plant-based.
Label detail 1: EPA and DHA per serving
The amount of fish oil is not the amount of omega-3; the EPA and DHA lines are the numbers that count. Fish oil is a mix of fats, and only part of it is the long-chain omega-3s EPA and DHA that research focuses on. The NIH Office of Dietary Supplements describes a typical fish oil supplement as about 1,000 mg of fish oil providing 180 mg of EPA and 120 mg of DHA, though amounts vary widely.
So a bottle that says "1,000 mg fish oil" on the front may provide far less omega-3 than that. Look for separate EPA and DHA lines in milligrams, add them together, and compare that total with the fish oil figure. If a label lists only "fish oil" with no EPA or DHA breakdown, you cannot judge what you are buying. For what each fat does, see our explainer on EPA vs. DHA.
Label detail 2: Serving size and how many softgels a day
Every figure on a Supplement Facts panel refers to one serving, which may be more than one softgel. A product that looks strong may need two or three softgels to reach the numbers printed on the panel. Read three lines together:
- Serving size, such as "2 softgels".
- Suggested use, which tells you how many servings a day and whether to take them with meals.
- Servings per container, which tells you how many days a bottle lasts.
With those three, you can compare products on cost per day and omega-3 per day rather than on the size of the bottle. For context on amounts, the FDA has concluded that supplements providing no more than 5 g a day of EPA and DHA combined are safe when used as recommended, and it specifies that labels should not recommend more than 2 g a day. Our guide on how much omega-3 per day covers this in detail.
Label detail 3: Freshness and form
Fish oil can oxidize, and studies of store-bought products have found many above recommended oxidation limits. A 2015 study of 171 omega-3 products sold in Canada found that half exceeded voluntary oxidation limits, and a 2015 New Zealand study found most fish oils tested had less EPA and DHA than their labels stated. The New Zealand researchers also found that best-before date, price and country of origin were poor guides to quality.
What you can check yourself:
- Best-before date and lot number. A lot number means a batch can be traced and tested.
- Smell and taste. A sharp, rancid smell is a warning sign. Some products add natural flavor, so smell is a rough check only.
- Storage. Keep fish oil in a cool, dry place with the lid closed.
The label may also name the chemical form of the omega-3s. According to the Office of Dietary Supplements, natural triglycerides, re-esterified triglycerides and free fatty acids are absorbed somewhat better than ethyl esters, but all forms significantly raise blood EPA and DHA levels. Many labels do not state the form at all, so it is a secondary detail.
Label detail 4: Fish source, allergens and the softgel
A fish oil label must declare the fish species as an allergen, and a gelatin softgel is not plant-based. Look for:
- The fish species. Small fish such as anchovy and sardine are common sources. A named species is a sign of a traceable supply.
- The "Contains" statement. Fish is a major food allergen, so it must be declared.
- The softgel material. Most fish oil softgels are gelatin, which may be bovine or porcine. That matters for some diets.
- Flavors and extras. Lemon or other natural flavors are common; some products add vitamins, as cod liver oil naturally contains vitamins A and D.
If you follow a plant-based diet or avoid fish, fish oil is not the right category; algae oil is. Our comparison of fish oil vs. algae oil explains the trade-offs.
Label detail 5: Third-party testing
Dietary supplements are not approved by the FDA before sale, and the studies above show that labels alone cannot be taken on trust. Independent testing by an outside lab checks identity, potency and purity, including oxidation and contaminants such as heavy metals. Testing every batch is a stronger standard than testing once.
Ask for the certificate of analysis (COA), the lab report for a specific batch. Our guide to how to read a supplement certificate of analysis shows what each line means. Also check the facility: GMP certification covers how the product is made, which is separate from batch testing.
A worked example: the five details on Pure Omega+
Here is how the five details read on the Pure Omega+ label.
| Label detail | What the label shows |
|---|---|
| 1. EPA and DHA per serving | 864 mg EPA and 576 mg DHA (1,440 mg omega-3) from 2,400 mg fish oil |
| 2. Serving size and daily count | 2 softgels per serving; two softgels daily with meals; 60 softgels, a 30-day supply |
| 3. Freshness | Store in a cool, dry place; natural lemon flavor |
| 4. Source and allergens | Contains: Fish (Anchovy). May contain porcine. Gelatin softgel, not suitable for a plant-based diet |
| 5. Testing | Third-party tested, every batch, for purity and potency |
Each Pure Omega+ softgel carries 1,200 mg of fish oil, and the two-softgel serving provides the full figures above. The other ingredients are gelatin, glycerol, water and natural lemon flavor. The fish oil is globally sourced and bottled in an NSF-certified, GMP-certified, FDA-registered U.S. facility; our standards page explains the testing. Pure Omega+ is formulated to contribute to a healthy heart, support joint flexibility, promote brain and nerve function, support vision health and aid in memory care.*
If fish oil leaves an aftertaste, taking it with meals as directed usually helps; our article on fish oil burps has more practical tips.
Safety notes
The Pure Omega+ label states: Do not exceed recommended dose. Pregnant or nursing mothers, children under the age of 18, and individuals with a known medical condition should consult a physician before using this or any dietary supplement.
The Office of Dietary Supplements notes that fish oil can have antiplatelet effects at high doses and may affect clotting time in people taking warfarin. If you take a blood thinner or any prescription medicine, talk with your healthcare provider first. Side effects are usually mild, such as an unpleasant taste, heartburn or an upset stomach.
Frequently asked questions about how to choose a fish oil supplement
What is the most important thing on a fish oil label?
The EPA and DHA amounts per serving. They tell you how much long-chain omega-3 you get, which the total fish oil figure does not.
Why does my fish oil need two softgels per serving?
Each softgel can only hold so much oil. When a label lists a two-softgel serving, the EPA and DHA figures on the panel refer to both softgels together.
How can I tell if fish oil has gone bad?
A strong, sharp or rancid smell is a warning sign, as is an expired best-before date. Testing is the only reliable check, which is why batch testing and a certificate of analysis matter.
Is fish oil suitable for vegetarians?
No. Fish oil comes from fish, and most softgels are gelatin. Algae oil is the plant-based source of DHA, and some algae oils also contain EPA.
Does the brand of fish oil matter?
What matters is what the brand can show: clear EPA and DHA amounts, a named source, honest allergen statements and independent testing of every batch. Studies have found that price and country of origin alone are poor guides to quality.
Related reading from our Wellness Hub
- Inside Pure Omega+: How to Read the Fish Oil, EPA, and DHA Numbers
- Best Time to Take Fish Oil: A Simple Omega-3 Routine With Meals
- How Much Omega-3 Per Day? EPA and DHA Amounts Explained
Sources
- NIH Office of Dietary Supplements: Omega-3 Fatty Acids, Fact Sheet for Health Professionals (typical amounts, forms, FDA limits, safety)
- Jackowski SA, et al. Oxidation levels of North American over-the-counter n-3 (omega-3) supplements. J Nutr Sci, 2015
- Albert BB, et al. Fish oil supplements in New Zealand are highly oxidised and do not meet label content of n-3 PUFA. Sci Rep, 2015
- National Center for Complementary and Integrative Health: Omega-3 Supplements, What You Need To Know
Individual results vary.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
