5 Ways Your Calcium Supplement May Interact with Medications

Calcium supplements may be a bonus for bone health. But if you’re taking these medications, your supplement might backfire.

Lauren is an award-winning registered dietitian, author of three books and all-around lover of good food. After graduating with a bachelor's degree in food science and human nutrition and a master's degree in clinical nutrition, Lauren has worked in various nutrition-related settings, most currently writing nutrition-related content for online outlets including Verywell Health, PopSugar, The Kitchn, and EatingWell. Additionally, she manages the Instagram page @LaurenLovesNutrition, where people can receive evidence-based nutrition tips and updates.

Karen Ansel, M.S., RDN, is a nutritionist, journalist and author. In her 20-plus years of experience, she has written hundreds of health-focused articles about food, nutrition, fitness and wellness. Her work has appeared in EatingWell, Women's Health, Weight Watchers, Men's Health, Shape, Woman's Day, Prevention, Fitbit and other publications and websites.

Abbey Littlejohn

Calcium is a vital mineral essential for strong bones and teeth. It also plays a role in various bodily functions such as muscle contraction, nerve transmission and blood clotting. However, most people don’t consume enough calcium-rich foods and may turn to calcium supplements to bridge the gap.

While calcium supplements can be beneficial, it's important to know how they may interact with certain medications. These interactions can alter the drug’s effectiveness or the absorption of calcium itself, potentially leading to unintended health consequences.

If you are taking calcium supplements, this article will tell you everything you need to know to avoid interactions with your medications.

Here are five medications that are most likely to adversely interact with calcium supplements.

One medication that may interact with calcium supplements is levothyroxine, commonly used to treat thyroid disorders. “Levothyroxine can bind to calcium carbonate in an acidic environment, which decreases its absorption into the bloodstream,” says Megan Huff, RDN, LDN, a registered dietitian and owner of Nutrition by Megan. This may reduce levothyroxine’s effectiveness, which may potentially require dosing adjustments to maintain optimal thyroid hormone levels.

It may also be necessary to adjust the timing of your medication. Taking levothyroxine on an empty stomach and several hours apart from calcium supplements can help minimize this interaction for proper absorption.

“Certain antibiotics, specifically those in the classes of tetracyclines and fluoroquinolones, may bind to calcium and negatively impact the effectiveness of the medication,” says Michelle Rauch, M.Sc., RDN, a registered dietitian nutritionist for The Actors Fund. “This binding inhibits absorption of the medication, making it less effective against infection.”

Examples of common tetracyclines include doxycycline and minocycline, while commonly prescribed fluoroquinolones include ciprofloxacin, levofloxacin and moxifloxacin, says Rauch.

Taking these medications several hours apart from calcium supplements may help mitigate this interaction and ensure they can be properly absorbed into the bloodstream.

Omeprazole, a proton pump inhibitor used to treat conditions like gastroesophageal reflux disease (GERD), is another medication that may be affected by calcium supplements. Omeprazole works by reducing stomach acid production, which may influence the absorption of various nutrients, including calcium. When calcium supplements are taken with omeprazole, the decrease in stomach acidity can impair the solubility and absorption of calcium, potentially impacting its effectiveness. If you take omeprazole and a calcium supplement, choose calcium citrate. Because it is less dependent on stomach acid for absorption, it is a better choice than other forms of calcium, such as calcium carbonate.

Thiazide diuretics are primarily used to treat hypertension and edema. These medications work by reducing fluid retention and lowering blood pressure. However, they can lead to increased calcium levels in the bloodstream. When additional calcium supplements are consumed, there is a risk of hypercalcemia, or high calcium levels, which can cause muscle weakness, fatigue and abnormal heart rhythms. As a result, regular blood tests may be advised to monitor calcium levels and adjust dosages to maintain safe ranges. If you take thiazide diuretics and are considering a calcium supplement, speak with your healthcare provider first.

Iron is an essential mineral that supports various bodily functions, including the production of hemoglobin. While iron is not technically a medication, calcium supplements may interfere with its absorption and decrease its efficacy. This interaction occurs in the gastrointestinal tract, where calcium competes with iron for absorption. Taking iron and calcium supplements at different times of the day may mitigate this interaction. For example, taking iron supplements in the morning and calcium supplements in the evening can help ensure optimal absorption of both nutrients.

Whether you are already taking a calcium supplement or considering adding one to your regimen, it's essential to proceed with caution, especially if you're already taking medications. Just because calcium is natural doesn’t mean that it is necessarily safe for everyone. The truth is that calcium can interact with certain medications, influencing their effectiveness or causing harmful side effects.

Keep in mind that just like calcium supplements, calcium-rich foods can also affect the absorption of certain medications. Before making any changes to your diet or adding calcium supplements to your routine, speak with a healthcare professional. They can offer personalized advice based on your health history and current medications to tailor the right plan for you. Additionally, a healthcare professional can conduct necessary tests to determine if you truly need a supplement or if dietary changes might be sufficient.

Your healthcare provider can also tell you which form of calcium to look for in your supplement. “Calcium supplements come in various forms, like calcium carbonate and calcium citrate,” says Rauch. “Certain forms are recommended for those who are on medications that impact stomach acidity,” she says. Since calcium supplements can block the absorption of certain medications, ask your provider about the optimal time to take each.

Even though calcium supplements can be purchased without a prescription, they can still impact the absorption and effectiveness of certain medications. This may alter their therapeutic effects, especially those that require precise dosing.

If you are considering a calcium supplement, it is important to engage in open communication with your healthcare provider, especially if you take prescription medication. This proactive approach can prevent complications and ensure that your medications work optimally.

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