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3 types of medications that could have a vitamin interaction

Lauren Steele writer headshot By | August 28, 2019
Medically reviewed by Anis Rehman, MD

Adding vitamins and supplements to your daily care regimen can help improve your general health and stave off ailments. But many don’t realize that vitamins and supplements can also affect prescription medications when mixed. According to a national Wakefield Research survey, nearly 40 percent of Americans who take prescription medications are unaware of vitamin interactions.

Vitamin interactions with antidepressants

The combination of SSRI and antidepressant medications with supplements can be especially dangerous. If you have an anxiety disorder or depression, your doctor may prescribe a selective serotonin reuptake inhibitor (SSRI). Common SSRIs are Lexapro, Prozac, Paxil, and Zoloft. These are safe for most people, but when taken with supplements or vitamins, the results can be risky. Brandi Cole, Pharm.D., a medical advisory board member for Persona Nutrition, explains why.

“Most SSRIs are extensively metabolized by liver enzymes, and supplements that affect these enzymes could potentially change the way your body eliminates SSRIs,” Cole says. “For example; St John’s Wort induces liver enzymes—meaning it makes the liver eliminate prescription drugs more quickly than normal.” Translation: Your system clears SSRIs sooner than intended, and without the correct amount of medication in your system, your medication can’t work. 

Additionally, some supplements can cause medication to interact negatively with your body’s systems and processes. Supplements that affect the heart’s rhythm (like cesium or ephedra) could cause a dangerously irregular heartbeat when taken with SSRIs. Supplements that contain serotonin or alter serotonin metabolism—such as 5HTP (a serotonin precursor), SAMe, or St John’s Wort can cause (the potentially life-threatening) serotonin syndrome when taken with SSRIs.

Vitamin interactions with birth control

But it’s not just SSRIs. If you are a woman who uses oral contraceptives for birth control, beware of St. John’s Wort. “St. John’s Wort can render contraceptive useless if you’re taking it regularly,” Cole says. “In fact, taking St John’s Wort can decrease norethindrone and ethinyl estradiol levels by 13% to 15%, which can result in an unplanned pregnancy.”

Iron supplements and antibiotics

Taking iron alongside antibiotics, such as ciprofloxacin, tetracycline, and minocycline, may decrease your body’s absorption rate of the antibiotic prescription. Additionally, those taking synthetic thyroid hormone replacement such as Levothyroxine should be sure to avoid all supplements that contain soy, iron, and calcium, which, “if taken within four hours of taking a synthetic thyroid hormone, may reduce the absorption rate,” Dr. Cole says.

Iron supplements may also interact with blood pressure medications called ACE-inhibitors and decrease their absorption.

These are a few examples of how supplements and medications can negatively impact one another, but how certain vitamin interactions (i.e., vitamin d interactions with steroids) can happen is largely a case-by-case basis. So always chat with your doctor or pharmacist before starting any new medication, vitamin, or supplement.

“Prescription medications can deplete nutrients from the body or provide additional nutrients based on the makeup of the medications you’re taking—and that can be helpful or hurtful,” Dr. Cole says. “That’s why it’s important to have an understanding of drug-nutrient interactions if you’re taking both supplements and prescription medications.”