3 Green Flags Your Multivitamin Is Working As It Should

The world of supplements can feel confusing, complicated, and just plain overwhelming. This leaves many of us reaching for something simple—a multivitamin—to cover all our bases in one fell swoop.

But if you're taking a multivitamin…how do you know it's actually doing its job? We chatted with Marvin Singh, M.D., a functional medicine physician and author of Rescue Your Health, to get our multivitamin questions answered, starting with the most obvious one: What are they and how can you tell if they're working? 

How do you know if your multivitamin is working? 

"A multivitamin is sort of like an insurance policy," says Singh. As he explains it, in an ideal world, we'd be able to get the minimum required nutrients from our diets in the form of food. But as we know, this isn't always possible.

For the times when we miss some nutrients (e.g., we go on a trip, we scarf down a granola bar for lunch, or we just don't have the effort to cook those leafy greens after work), a multivitamin can help fill in any gaps.

The goal of this is to make sure you're not developing a deficiency in any one nutrient, which is increasingly common. According to the CDC's Second Nutrition Report, just under 10% of the U.S. population had a nutritional deficiency. This depends on a lot of factors like age, gender, and ethnicity, and that number could be as high as 30% in certain populations.

If you're ready to click "purchase" on a multivitamin, there's one thing to know first: They're not all created equal. "I try to find a multivitamin from a high-quality company with a good reputation," says Singh.

According to him, some green flags are using organic ingredients, natural flavorings and colorings, and products that are free from fillers, dyes, and gluten.

Once you've found a high-quality product, you might wonder how long it takes before you know it's working.

There aren't any hard-and-fast rules, but experts recommend waiting anywhere from a few weeks to a few months before expecting a change. And even then, according to Singh, you're unlikely to notice anything too drastic (but that doesn't mean your supplement isn't doing its job).

That's because multivitamins are meant to supply a little bit of a lot of different nutrients to maintain healthy levels versus actually correcting a deficiency. If you have a true deficiency, a multivitamin likely doesn't contain enough of that nutrient to correct it.

For example, if you have a vitamin D deficiency, doctors recommend taking at least 5,000 IUs of vitamin D a day to correct a deficiency versus just maintaining healthy levels. Why? Because according to certified clinical nutritionist Lindsay Boyers, it takes 1,000 IU of vitamin D3 per day to increase your levels1 by about 10 ng/ml4, but the typical multivitamin only contains about 400 IUs of vitamin D. 

That said, there are some hints that your multivitamin is working: 

Singh reminds us to always mention any supplements you're taking to your doctor. "For most people, however, a multivitamin isn't something problematic to take unless you have high levels of a particular vitamin already (in which case taking more might not be a good thing for your health)," he explains. That said, it's always good to play it safe.

The takeaway

A multivitamin is a great addition to a healthy diet, but it can be tricky to tell if yours is actually "working."

While its impact is often subtle, a good multivitamin may help you feel more energized, clearheaded, and free of deficiencies.