There are some over-the-counter (OTC) medications that may be part of your daily routine, like taking melatonin every night before you go to bed or a multivitamin in the morning. Then there are the over-the-counter meds you take only when you need them, like when you have a headache or nasal congestion.

OTC meds can be a godsend. Imagine if you had to see a doctor and get a prescription every time you got period cramps or an irritating cough. But just because you don’t need to see a doctor to get them doesn’t mean you shouldn’t take OTC meds seriously. When taken incorrectly, over-the-counter medications can negatively impact health.

Some OTC medications are dangerous when taken together. In fact, there are two medications in particular that doctors say can be especially bad to take together.

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2 Over-The-Counter Medications You Should Never Take Together

If you have a fever or are experiencing pain, it can sound like a good idea to take both Tylenol and NyQuil. That way, you have something to reduce your fever or pain as well as help you sleep better. But Dr. Brynna Connor, MD, a family medicine doctor and a healthcare ambassador at NorthWestPharmacy.com, says taking these medications together is a bad idea.

“Both products contain acetaminophen. People are, without realizing it, double-dosing,” Dr. Connor says. She explains that the liver can only process so much acetaminophen in 24 hours. “A maximum of 4,000 milligrams for a healthy adult, and frankly, I tell most people to stay well under 3,000 milligrams,” she says. “Exceeding that, even for a day or two, can cause severe, irreversible liver damage. It’s a remarkably fast track to liver failure, and people do it all the time.”

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On a similar note, Dr. Parth Bhavsar, MD, a family medicine doctor and the founder of TeleDirectMD, says that combining NyQuil and Benadryl can also be dangerous. He explains that taking them together can cause intense drowsiness, confusion, blurred vision and slowed breathing. Dr. Bhavsar adds that taking them together can also increase the risk of falling or experiencing morning-after grogginess.

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Dr. Gerda Maissel, MD, BCPA, CPE, the president of My MD Advisor, also warns against taking Benadryl and sleeping medications, like Tylenol PM, together. “Both contain diphenhydramine. Not only are you taking the same medication at a higher dose than intended, but the active ingredient can cause memory loss, urinary retention, dizziness and lead to falls, especially in higher doses,” she says.

Other Safety Tips To Keep in Mind When Taking Over-The-Counter Medications

All three doctors emphasize that it’s important to read a medication’s directions before taking it—even if it’s a medication you’ve taken in the past. If you are taking more than one OTC medication, Dr. Maissel says it’s important to read the ingredients list and avoid taking medications that have any overlapping ingredients together.

She says this goes for supplements too. “I had one patient who took vitamin D, plus a multivitamin, an osteoporosis supplement and an ocular health supplement, all of which contained vitamin D. Her vitamin D levels were way too high,” Dr. Maissel explains.

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If you have a cold and want to take OTC meds to relieve your symptoms, Dr. Bhavsar says to pick one medication or look for a medication that treats more than one symptom. For example, if you want to take an antihistamine and a cough reliever, she says to find one medication that helps on both fronts instead of taking two different medications. If you have any questions about OTC meds, she says to consult a pharmacist.

In general, Dr. Connor says it’s not recommended to drink alcohol when taking over-the-counter medications either.

“I see people land in the emergency room after combining acetaminophen and alcohol, one of the worst combinations,” she warns. “Both acetaminophen and alcohol are processed by the liver. When you combine them, you are overwhelming the liver’s processing pathways, which creates a highly toxic byproduct that destroys liver cells. Even a moderate amount of alcohol combined with a correct dose of acetaminophen can be dangerous.”

All three doctors emphasize that OTC meds should be taken seriously. “My most practical piece of advice is to stop treating over-the-counter drugs like candy just because you don’t need a prescription. They are serious chemicals with serious consequences,” Dr. Connor says. If you are taking more than one medication, she reiterates the importance of making sure none of them contain the same ingredients.

“Your body is not a test lab. Your liver and your stomach lining aren’t replaceable parts. When in doubt, walk to the pharmacy counter and ask the pharmacist. A 10-second question is worth avoiding a ten-day hospital stay,“ Dr. Connor shares. After all, that’s what pharmacists are there for. Don’t be afraid to ask for guidance.

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Sources:

Dr. Brynna Connor, MD, family medicine doctor and a healthcare ambassador at NorthWestPharmacy.com

Dr. Parth Bhavsar, MD, family medicine doctor and the founder of TeleDirectMD

This story was originally reported by Parade on Nov 8, 2025, where it first appeared in the Health & Wellness section. Add Parade as a Preferred Source by clicking here.