The classic dissolve test: drop a multivitamin in warm water and stir for 30 minutes…  

What does that really say about that pill’s ability to be digested anyway? Since your stomach is basically a warm pouch for food to churn around a while, the home test is a decent illustration of how that pill will breakdown in your stomach. But it’s not the full picture since digestion goes beyond the stomach and it doesn’t work for time-released, enteric coated or chewable tablets and capsules. 

Here we give expert advice on when and how (with food vs. on an empty stomach) to take the most popular daily supplements so you can reap the benefits of optimal absorption. 

A traditional multivitamin/mineral containing only 100% the RDAs (except >250 mg calcium or magnesium) should not present any digestion or absorption issues for adults with healthy guts.

Most individual micronutrients are better absorbed when taken in small doses at mealtimes, though B vitamins should be taken on an empty stomach. Fat-soluble vitamins (A, D, E and K), magnesium and iron are best taken with food to maximize absorption and minimize gastrointestinal upset. 

Note that calcium, zinc and iron compete for absorption, so it’s best to take them at least two hours apart from one another. Consider pairing these individual supplements or getting them in combination: vitamin C helps iron absorption (particularly plant-based non-heme iron); and vitamin D aids calcium absorption. Unpaired calcium citrate is okay on an empty stomach. 

Most people take their multivitamin/mineral supplement in the morning instead of at night. “Digestion slows down during sleep, so taking your nutrient supplement late at night would not be associated with an efficient absorption,” as told to The Washington Post by Jeffrey Blumberg, PhD, a professor of nutrition at Tufts University. Taking your supplement when you start your day with a routine also helps increase consistency.

Fish oils (contains omega-3 EPA and DHA fatty acids) are generally better absorbed when taken with meals containing fat as that prompts the secretion of enzymes and bile salts needed for fat digestion. Plus, they can cause digestive upset on an empty stomach and produce “fish burps,” so taking them with food helps relieve or mask these effects. 

Fiber supplements by their chemical nature aren’t ‘digested;’ they’re fermented in the large intestine. As with most supplements, they should be taken with a glass of water.

If the intent is to promote fullness, lower cholesterol or moderate blood sugar levels, a powder form of soluble fiber consumed with food will slow initial digestion.

To relieve constipation as a stool softener or bulk-forming laxative, taking fiber at night is ideal because of its longer time to work while sleeping. So, taking fiber with your evening meal works for whichever form of fiber supplement you’ve got.