It’s probably the most widely used sleep supplement available, and at about five bucks for a month’s supply, it’s our pick for cheapest. But tales of overuse and unusual side effects make melatonin a not-so-straightforward choice. Here, we’ll clear up a few things—plus share some lesser-known facts about this ubiquitous sleep remedy.

It doesn’t just come in pill form.

Melatonin can be taken in tablets, capsules, liquid, and even in patches that transfer the hormone via your skin.

And you can get melatonin from your food.

Few foods actually contain melatonin, but tart cherries (especially Montmorency cherries) are a surprisingly good source of the stuff, and a few studies have confirmed its presence in grains like wheat, barley, and oats. (Some people even bake it into cakes and sell them as relaxation aids!)

While they might not actually contain melatonin, there’s also evidence that bananas and (to a much lesser extent) oranges and pineapples can lead to increased serum melatonin levels. And given that bananas are also packed with potassium and magnesium, two natural muscle relaxants, this makes ‘em a great bedtime snack!But the most important way to control your melatonin is light.

Everything from your brain activity to your exercise performance is influenced by your circadian rhythm, an internal clock that responds predominantly to light and darkness, and your melatonin production is no different.

Want your body to keep this sleep-inducing hormone low during the day and high as you approach bedtime? Use a dimmer switch and table lamps as your day winds down, invest in some blackout curtains to keep your room, well, blacked out, and try to prevent your phone, digital clock, and other electronics from illuminating the darkness.

It’s not just used for better sleep.

Melatonin is actually an antioxidant, (and a pretty powerful one at that), so it protects against free radicals that can cause cancer, stroke, and heart disease. A July 2015 study in theJournal of Pineal Research, for example, concluded that melatonin may be an effective way to prevent various forms of heart dysfunction. It’s also been shown to be a really effective supplement for people undergoing chemotherapy. In some cases, it’s led to substantial improvements in tumor remission, alleviation of chemo side effects, and even overall survival rates.

It can have some funky side effects.

It’s a sleeping pill, but drowsiness isn’t the only side effect. Among some people it can lower body temperature, alter blood pressure, decrease libido, or induce stomach cramps.

And then there are the widespread reports that it gives you vivid, crazy dreams. Which is just another reason why…

You really shouldn’t take it without talking to a doctor.

It’s freely available over-the-counter, but melatonin may cause harm in combination with certain medications. Antidepressants and sedatives in particular appear to interact negatively with the drug, but even the common birth control pill affects the body’s production of melatonin and might give your system a surplus when used in combination. Diabetes meds, blood-thinners, and medications that suppress the immune system (common for folks on the receiving end of organ transplants) can also make cavalier melatonin dosing a very bad idea.

Unless you’re perfectly healthy and don’t use any medications, talk to your doctor before popping pills. And if you do decide to experiment with melatonin, start slow: begin with a dosage of 0.5 milligrams and gradually increase it until you find what works for you.