How to Take Vitamins and Cold Medicine Together

Mixing medications and dietary supplements can be a recipe for disaster. Certain vitamins and minerals could cause dangerous drug interactions, putting your health at risk. If you have a cold, see your doctor before popping pills.

Vitamin C, for example, may interact with aspirin, acetaminophen (Tylenol) and other cold medications. Calcium and iron supplements don't work well with some antibiotics. Stay on the safe side and avoid mixing medications unless the doctor recommends it.

Millions of Americans are misusing or abusing prescription medications. More than 80 percent of older adults take at least one prescription drug daily, according to the National Institute on Drug Abuse. About half of them use at least five prescription drugs or supplements on a daily basis.

Furthermore, about 68 percent of the population takes dietary supplements, as reported by the Council for Responsible Nutrition. Multivitamins, vitamin C, vitamin D and calcium are among the most popular choices. Don't assume that over-the-counter (OTC) medications and supplements are safe, however. These products may contain doses of certain nutrients that are significantly higher than the daily recommended allowance.

These numbers show that most Americans take both prescription meds and dietary supplements. Sometimes, this combo can be harmful. Prescription and OTC drugs can interact with each other as well as with certain vitamins, minerals and antioxidants. These interactions can either increase or inhibit the action of one of the medications you're using.

Read more: Can I Take Vitamins If I Am Taking Antibiotics?

The Food and Drug Administration warns against mixing supplements and medications. Certain dietary supplements, including multivitamins, can interfere with your body's ability to absorb, process or eliminate medications. For example, taking multiple blood thinners, such as vitamin E, aspirin and warfarin, may cause internal bleeding or even stroke.

Vitamin supplements may interact with blood thinners too, according to the American Heart Association. Vitamin K, for instance, promotes blood clotting and should not be combined with blood thinners, antibiotics and drugs that reduce or block fat absorption, such as orlistat, commonly marketed as Alli and Xenical.

Both vitamin supplements and medications can help you get over a cold faster. Vitamins may also help prevent this condition in the first place by keeping your immune system strong. Just make sure you're aware of any potential interactions.

Vitamin C, for example, is the primary ingredient in dozens of cold medications, such as Emergen-C. This nutrient supports immune function and may help reduce cold duration, according to the U.S. National Library of Medicine. Unfortunately, it doesn't work for everyone, with effects that vary from one individual to another.

Read more: How Does Emergen-C Work and Are There Any Side Effects?

A research paper published in the Cochrane Database of Systematic Reviews in January 2013 assessed the effects of vitamin C on common cold incidence, duration and severity. Most studies and clinical trials had mixed results.

As the scientists note, vitamin C supplements are unlikely to lower your risk of catching a cold, but they may shorten the duration and severity of colds in some people. Surprisingly, they may cut the risk of having a cold by half in athletes and active individuals, but not in the general population.

Read more: 12 Not-So-Common Tips to Fend Off Cold and Flu

The downside is that vitamin C may interact with several medications, including cholesterol-lowering drugs and chemotherapy drugs, antiviral drugs, warfarin, estrogen-based birth control pills, and medications containing aluminum. Furthermore, it may cause aspirin to accumulate in the body, according to the University of Rochester Medical Center. Certain antibiotics, especially those containing tetracycline (marketed as Tylenol) may reduce the efficacy of vitamin C.

If you have a cold, let your doctor know about any medications you're currently taking. Your doctor can determine whether or not it's safe to take vitamin C and prescribe the appropriate dosage.

You probably know that vitamin D keeps your bones strong and protects against bone diseases. This fat-soluble nutrient improves your body's ability to absorb calcium, supports immune function and modulates cell growth. What you may not know is that it also protects against colds, as reported in a systematic review published in the BMJ in February 2017.

The researchers found that vitamin D supplementation may help prevent acute respiratory tract infections, such as pneumonia and bronchitis. It appears to be particularly beneficial for people with low vitamin D levels. This nutrient strengthens the immune system and protects against respiratory pathogens.

Another study, featured in the journal Pediatrics in September 2012, suggests that vitamin D supplements may significantly lower the risk of acute respiratory infections in children who are deficient in this nutrient.

Again, there is a risk of drug interactions. The Mayo Clinic points out that vitamin D may interact with certain heart medications, steroids, laxatives, diuretics, anticonvulsants, and blood pressure and anti-obesity drugs. For example, taking large doses of vitamin D along with digoxin, a medication prescribed for irregular heartbeat and other cardiovascular problems, may cause high calcium levels in the bloodstream and lead to fatal heart problems.

Some cold medications and multivitamin formulas contain zinc, a mineral that contributes to over 100 enzymatic reactions in the body. Zinc plays a crucial role in protein synthesis, growth and development, cell metabolism and immunity.

This essential nutrient may also shorten the duration of the common cold, especially when used in higher doses, according to a July 2012 meta-analysis published in the Canadian Medical Association Journal (CMAJ). In clinical trials, zinc has been proven effective against respiratory viruses, although more research is needed to confirm its effects. As the researchers note, zinc supplementation may reduce cold duration and severity in adults but has a lesser impact on children.

Zinc syrup and lozenges appear to be more effective than pills, as the Mayo Clinic notes. Beware that high doses may cause nervous system damage and interfere with copper absorption, among other side effects. On top of that, zinc can interact with antibiotics, diuretics and some drugs prescribed for arthritis.

It's clear that mixing medications and dietary supplements or cold remedies isn't a good idea. To stay safe, discuss your options with a doctor or pharmacist. Read the product label and check for any potential interactions and side effects. Consider taking cold medications and vitamin supplements at different times of the day to lower the risk of adverse reactions.

Use the Rxisk Interaction Checker, the Memorial Sloan Kettering Cancer Center database or any other drug-to-drug interaction chart, especially when taking new medications or supplements. Keep a list of all drugs you use and check it with a pharmacist. Remember to include any over-the-counter medications, supplements and herbal products you take — not just prescription drugs.

The more medications you take, the higher the risk of side effects and interactions. Simple things, such as using a pill organizer and following your doctor's instructions, can help mitigate these risks. Also, don't take any medications you don't need. Always use the lowest effective dose and increase it gradually (if necessary).