Omega-3 and Magnesium: Best Time to Take

Quick answer

No source we read describes fish oil and magnesium affecting each other. Both can upset the stomach at higher amounts, and a meal helps each: fish oil is absorbed better with fat, and urine magnesium rose more with meals in a pilot study. Magnesium from supplements is limited to 350 mg a day.^1,2,3

Key facts

Neither the NIH omega-3 sheets nor the magnesium sheets describe one changing how the other is absorbed.^4,5
A high-fat meal raised EPA absorption from fish oil from 69% to 90%, and in a pilot study of eight adults urine magnesium rose by 33.6 mg a day when taken with meals against 21.8 mg when fasting.^1,2
The upper limit for magnesium from supplements and medicines is 350 mg a day. No upper limit is set for EPA and DHA, and FDA considers up to 5 g a day safe.^3,6
Seafood supplies magnesium along with omega-3s, vitamin D, calcium, potassium, iron, choline and iodine.⁴
The only magnesium timing in our ingredient file comes from a sleep trial, where 250 mg as bisglycinate was taken 30 to 60 minutes before bed.⁷

What the sources say about taking the two together

We looked for any statement that magnesium changes how fish oil is absorbed, or that fish oil changes how magnesium is absorbed. The NIH fact sheets for omega-3 fatty acids and for magnesium contain none, and we found no trial of the pair. The two have different jobs: omega-3s are fats the body builds into cell membranes, and magnesium is a mineral that helps more than 300 enzyme systems.^4,5

What the sources do give is a way to think about the day. Each supplement has its own best conditions, and the question is whether those conditions overlap. They do, mostly, at a meal.^4,8

What each is graded for

Provides EPA and DHA, which contribute to normal heart function*^4,9,10

Moderate evidence

This is the nutrient-function statement authorized in the EU, on condition that the daily intake is at least 250 mg of EPA plus DHA. It rests mainly on studies linking fish and omega-3 intake with heart health. It is not a promise of fewer heart problems: in the 25,871-person VITAL trial, about 840 mg a day did not improve the trial's main heart outcome.

Amount studied: At least 250 mg of EPA plus DHA a day, the EU condition for this statement

Helps you reach the recommended daily magnesium intake*⁵

Moderate evidence

National survey data from 2013 to 2016 show that 48% of Americans take in less magnesium from food and drink than the estimated average requirement. One serving supplies 275 mg, 65% of the Daily Value. In an earlier national survey, adults who used magnesium supplements had average total intakes well above requirement levels.

Amount studied: Recommended intake: 400 to 420 mg a day for men, 310 to 320 mg for women, from all sources

Best time to take fish oil and magnesium

What the studies say about timing^{1,2,7,8,11,12,13}
	Fish oil	Magnesium
Food	Absorbed better with a meal that contains fat	Urine magnesium rose more when taken with meals than when fasting, in a pilot of eight adults
Dose size	A prescription omega-3 medicine may be taken at once or in two doses	Absorbed better from several small amounts than from one large amount
Time of day	None named	A bedtime dose of 250 mg as bisglycinate was used in one sleep trial
How long it takes	Red blood cell levels need about 180 days to level off	Blood levels leveled off after about 20 weeks in a pooled analysis

The only place the two could diverge is the evening. The magnesium sleep trial used a bedtime dose, while fish oil is absorbed better with a meal. If you want a single time that satisfies both, an evening meal with some fat is consistent with the sources. If you prefer separate times, nothing we read advises against that either.^1,7

Telling their stomach effects apart

Both supplements can unsettle the stomach, and the effects overlap, which makes it hard to know which one is responsible. NIH describes the usual fish oil complaints as an unpleasant taste, bad breath, heartburn, nausea and stomach discomfort. For magnesium the pattern is loose stools, nausea and cramping, and in Cochrane trials those effects affected 11% to 37% of people taking oral magnesium against 10% to 14% on placebo.^3,6,14

Diarrhea is listed for both, so it cannot tell you which one is responsible. Taste changes, bad breath and burping are the fish oil complaints that have no counterpart in the magnesium sources. For magnesium, the form matters, since oxide, carbonate, chloride and gluconate are the ones most often reported to cause diarrhea.^5,6,11

Amounts and our products

What’s in ours

Omega-3: Fish oil concentrate, 1,000 mg per serving, from the label

What’s in ours

Magnesium Glycinate: Magnesium, 275 mg per serving, from the label
Men's Multi: Magnesium, 50 mg per serving, from the label
Creatine + Electrolytes: Magnesium, 60 mg per serving, from the label

Our Omega-3 is two softgels a day. Magnesium appears in several of our products and the 350 mg limit counts all of them. If you use more than one, check the product pages.³

Medicines and who should ask first

For fish oil, NIH says high doses of omega-3s may cause bleeding problems when taken with warfarin or other anticoagulants. Across seven large trials, omega-3 supplements were associated with more cases of an irregular heart rhythm, more so above 1 g a day than at 1 g or less.^6,15

Ask your pharmacist how far apart to take them

Supplements and medicines rich in magnesium can reduce the absorption of oral bisphosphonates such as alendronate. The alendronate label says calcium, antacids and oral medicines containing minerals such as magnesium interfere with its absorption.^3,5,16

On the medicine's label

Ask first if you take warfarin or another blood thinner, or an antiplatelet medicine such as aspirin, or have a bleeding disorder.^4,6
Ask first if you take an antibiotic, a bisphosphonate, a diuretic, a medicine for acid reflux, gabapentin or levothyroxine, each of which magnesium can affect.^3,5
Ask first if you have kidney disease or reduced kidney function, since the kidneys remove extra magnesium.⁵
Ask first if you are allergic to fish or shellfish, or have atrial fibrillation or another heart rhythm problem.^4,11
Ask first if you are pregnant or nursing, or under 18.^3,6

Questions people ask

Can you take omega 3 with magnesium?

The sources we read describe no effect of one on the other. Both can unsettle the stomach at higher amounts, so a meal and moderate amounts are sensible. Ask a pharmacist if you take a blood thinner or any of the medicines magnesium can bind.^4,5

Can you take fish oil with magnesium glycinate?

No source we read warns against it. Magnesium glycinate is one form of magnesium and its label amount is the magnesium itself, so count it toward the 350 mg limit like any other form.^3,5

What is the best time to take fish oil and magnesium?

Our sources set no hour for either. A meal with some fat suits fish oil, and magnesium was absorbed more with meals in a pilot study. A bedtime magnesium dose was used in one sleep trial.^1,2,7

Which causes more stomach upset?

Both can. Magnesium side effects were reported by 11% to 37% of people taking oral magnesium against 10% to 14% on placebo in pooled trials, and fish oil causes mostly mild effects such as taste, heartburn and nausea.^6,14

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See the Full Measure line Creatine + Electrolytes Magnesium Glycinate Men's Multi

Sources

*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.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.