Do you pop supplements like jelly beans? When it comes to the vitamins and minerals your body needs to function properly, you might think you can’t get too much of a good thing—especially when they’re wrapped in foil and taste like candy. But just like wine spritzers and apple crumble, you can overdo it on supplements.

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They’re complicated: More is not always better—and more can sometimes be dangerous. Vitamins, mineral supplements and even some herbs can interfere with each another, interact with the medications your doctor prescribes and it’s even possible to overdose on them. (We’re not talking about a scene out of the movie “Pulp Fiction” here, but the effects can be serious nonetheless.)

Before you down another multivitamin full of everything from A to Z, read on to find out which ones can spell T-R-O-U-B-L-E.

1. Calcium
To support bone strength, stave off osteoporosis and keep your muscles and joints working well, it’s important to get enough calcium in your diet. And that’s where most of it should come from: your diet! Calcium is available in a slew of foods, including the usual suspects, milk, cheese and yogurt, and less obvious places, such as dark leafy greens, sardines, soybeans, broccoli, sesame seeds and almonds. Aim for 1,300 mg a day, and get at most 50 percent from multivitamins and calcium chews. A recent study found that getting too much calcium (more than 1,400 mg daily—especially if more than half comes from supplements) can increase the risk of death from cardiovascular disease and prostate cancer (and what goes for prostate cancer usually ends up being the same for breast cancer). And don’t forget to move! Exercise, especially resistance work, is a key piece of the prescription for healthy bones.

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2. Vitamin B
We’re all tired and looking for a way to get more out of each day, so it’s no wonder that energy drinks are practically spilling out of store refrigerators wherever you go. We know that most of them contain caffeine and a lot of them tout B vitamins—niacin (B3), pantothenic acid (B5), B6, biotin (B7), folate (B9) and B12—which help your body generate energy from your food. Well, just because the label screams Healthy vitamins!! doesn’t make it a healthy beverage. Regularly downing energy drinks puts your at risk of going over your daily intake of B vitamins, which can cause nausea, hives, vomiting, mental dysfunction, nerve damage and liver issues not too far down the road. Skip the energy drinks and bulk up on better bets for B: peppers, cabbage, asparagus, spinach, clams, mushrooms, caffeinated water, tea and coffee.

3. Vitamin C
Vitamin C does so much—it’s the ultimate immune-booster and a total beauty nutrient. It helps prevent wrinkles, keeping skin firm and full, and it is great for your hair. It’s not too hard to find, and because it’s water soluble, vitamin C doesn’t get stored in your fat cells and build up there. But that doesn’t mean you can’t overdo it. Too much C over time can cause kidney stones and some data suggest that more than 2,500 mg a day can increase your chances of osteoarthritis. We recommend 800 mg (unless you’re taking statin drugs for high LDL cholesterol, in which case you should go even lower on C). You want to get your daily dose, but don’t go C-razy.

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4. Vitamin A
Like vitamin C, vitamin A is a powerful and important ingredient in many beauty foods, like milk, carrots, spinach, kale and cantaloupe. It’s especially great for skin and eyes and you should strive for up to 2,500 IU per day. But stop there. An overabundance of A can cause headaches, nausea and vomiting. It also causes fat to be stored in the liver—and is especially problematic if it comes from pills instead of food.

5. Iron
Another liver (and heart) taxer is iron. You want to get about 18 mg per day from dark leafy greens, beans, lentils, oysters, raisins and lean red meat. Iron is essential in the body because it helps your blood transport oxygen to where it’s needed most—that includes your vital organs as well as your skin and scalp. Without enough of it, your immune function, energy levels and beauty suffer (think bruises, hair loss and dark circles). But if your iron stores get overloaded, it can cause seriously toxicity and liver damage. It’s easy to get too much iron if you take a supplement, especially if you eat meat, so avoid any multivitamin that contains iron unless directed by your physician.

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The bottom line:
Think of supplements as an insurance policy. It’s best to get your nutrients from food, but if you don’t eat perfectly (and who does?) they’re a good back up. Your first step: Get a blood test at your yearly physical and talk to your doctor about the extra nutrients you need based on your results. Make sure they are aware of all prescription drugs and supplements you’re taking, to be sure everything works effectively and safely together.