Have you ever acted as your own personal pharmacist and mixed medications for a more powerful punch? Perhaps you didn’t get enough relief from one, so you decided to add in another thinking that should do the trick. I’ll be the first to point a finger – at my husband. I remember one time he took a leftover antibiotic, added some cold medicine for good measure and topped it all off with a few pain relievers – all to try to alleviate a bad head cold. Well, guess what? It didn’t help. He actually ended up feeling worse and proceeded to vomit a few hours later. And do you think he learned his lesson?

No.

While I can make light of my better half’s stubbornness, mixing medications is no laughing matter. In fact, dangerous dosages became top of mind for much of the country and across the world with the sudden death of young actor Heath Ledger, who recently passed away after reportedly mixing prescription medications that had an adverse effect. Ledger’s mistake is not uncommon: fatal accidental drug overdoses are on the rise, according to the Centers for Disease Control and Prevention.

Fatal combinations aside, mixing different medications and supplements can also cause allergic reactions, nausea, vomiting (sound familiar, honey?) and a host of other health concerns.

Don’t let a harmful mix-up happen to you. Follow this advice:

Know what you’re taking. Many people who take several medications for different health conditions lose track of what exactly one does that the other may not. Read the labels of all of the medications you’re taking, and ask your doctor or pharmacist to explain what the active ingredients are and how they work, or do you own research on the Internet or at your local library.

Tell your doctors about all your medications. If you see a variety of medical professionals for different reasons—say, for example, an internist for general health concerns, an endocrinoloigist to manage diabetes, and an opthalmologist to treat glaucoma—you may fill prescriptions from each one, and they may not be aware of everything else you’re taking unless you tell them. A good rule of thumb: write down the names and amounts of everything you take and bring that list with you to all of your doctor’s visits. Ask the receptionist to make a note of all your medications in your chart, and alert them to any changes. Don’t forget to include herbal supplements, as some can have adverse effects when combined with prescribed medications.

When in doubt, toss it out. Medications and supplements can be even more harmful if combined and ingested past their expiration date (cue leftover antibiotic). Pay close attention to when pills, powders and liquids are set to expire. If there is no expiration date and you can’t remember when you bought it, throw it away and ask if you need a new prescription. The same goes for vitamins and herbal supplements, especially if you notice a change in texture, appearance or smell.

Don’t underestimate the power of OTC. Even over-the-counter combinations can be harmful, so be careful when self-medicating for conditions like colds, headaches, insomnia and upset stomachs. And never take more than the recommended dose unless doing so has been approved by your doctor.

So, next time you want to play pharmacist, stop to consider the consequences. Mixing medications is a dangerous game – one you don’t want to lose at.