Walk down the health aisle of any pharmacy or grocery store and you'll see shelves packed with supplements promising everything from better sleep and stronger immunity to constipation relief and diabetes control. With so many options, it's easy to wonder: Should I take this? How do I know if it's effective? And is it safe?

The Food and Drug Administration (FDA) defines dietary supplements as products that include dietary ingredients, such as vitamins, minerals, herbs, amino acids and enzymes. These are often sold as pills, liquids, powders, gummies and more.

But buyers beware! It's essential to do your homework before adding a supplement to your daily routine. Here are five things to consider:

Supplements aren't regulated like medications

You might assume that if a supplement is sold in a store, it must be safe and effective. But unlike over-the-counter and prescription drugs, supplements don't undergo the same rigorous testing and approval process.

"Anything that's not a drug regulated by the FDA falls into the supplement category," says Dr. Kyle Mueller, a primary care doctor at Houston Methodist. "Because supplements are not intended to treat diseases or health conditions, they are not required to go through the rounds of clinical and safety trials that over-the-counter and prescription medications are put through."

This lack of oversight and regulation means manufacturers aren't required to prove their product is effective. This isn't to say supplements never work.

"There are roles for multivitamins and other vitamin and mineral supplements depending on the situation," adds Dr. Mueller.

For instance, people who have undergone the weight loss procedure bariatric surgery may require a multivitamin and other supplements to prevent certain nutrient deficiencies. And if blood testing indicates you're deficient in vitamin D, your doctor may recommend taking a vitamin D supplement.

Beware of bold claims

If a supplement claims to be a miracle cure, proceed with caution. "There is no supplement that is going to cure diabetes or cancer," says Dr. Mueller. "Any product making a claim like that is at best an exaggeration and, at worst, a complete falsehood."

By law, supplement labels can't claim to treat or cure diseases. Instead, they promise vague improvements such as "promotes circulation" or "supports immune health." These claims often simply allude to limited evidence about a specific ingredient rather than a proven health outcome. (Related: Do Multivitamins Actually Do Anything?)

And keep in mind that marketing buzzwords like "superfood" or "all-natural" can be misleading, too. "Just because something is natural doesn't automatically make it safe, not to mention effective," adds Dr. Mueller.

Supplements can interact with medications

Supplements aren't safe for everyone. Certain ones can interfere with medications in serious ways — either making a medication less effective or increasing its potency to a dangerous level.

"For example, St. John's Wort can make birth control and blood thinners less effective," says Dr. Mueller. "And gingko biloba can interfere with blood thinners and platelet medications, increasing the risk of bleeding."

Also dangerous: Some people stop taking prescribed medications in favor of a supplement. Dr. Mueller stresses that a supplement is never a replacement for a necessary medication.

"I've had patients who swap their diabetes medication for a supplement, only to see their condition worsen," says. Dr. Mueller. "It's critical to always consult your doctor before stopping a prescription medication."

Not all supplements contain what they claim

Because supplements aren't closely regulated, what's on the label may not actually match what's in the bottle.

For instance, a 2017 study tested over 30 different melatonin supplements and found that the actual melatonin content varied widely — some had 83% less than what was listed on the label; others contained up to 478% more. What's more, one-quarter of tested melatonin supplements contained ingredients other than melatonin. (Related: Is It Bad to Take Melatonin Every Night?)

"These are issues that can affect the side effects a person experiences, as well as the product's overall safety," Dr. Mueller warns.

Some supplement brands voluntarily seek third-party testing to verify their contents. If you do choose to take a supplement, do your research and look for products that have been certified by an independent third party laboratory, such as ConsumerLab, NSF or USP.

Alert your doctor of any supplements you're taking

"If a supplement is safe, affordable and a quality product, a short trial period can help determine whether it's worth taking on a routine basis," says Dr. Mueller. "If you don't see any improvement — or worse, you begin to experience side effects — it's not worth your money or your health to continue taking."

He also emphasizes the importance of keeping your doctor informed of the supplements you're taking — including how much — to ensure they don't interfere with existing medications or health issues.

"Lastly, know that supplements aren't a replacement for a healthy diet, and remember that a supplement can never replace a necessary medication," Dr. Mueller adds.