Drugs Q & AMedicines

How Calcium Supplements Affect Your Medications

Calcium supplements are available in the form of calcium carbonate (e.g., Tums) or calcium citrate (e.g., Calcitrate), or as part of other health supplements, such as multivitamins.  There are different kinds of calcium compounds used in calcium supplements. Each compound contains varying amounts of the mineral calcium — referred to as elemental calcium. Common calcium supplements may be labeled as:

  • Calcium carbonate (40% elemental calcium)
  • Calcium citrate (21% elemental calcium)
  • Calcium gluconate (9% elemental calcium)
  • Calcium lactate (13% elemental calcium)

The two main forms of calcium supplements are carbonate and citrate. Calcium carbonate is cheapest and therefore often a good first choice. Other forms of calcium in supplements include gluconate and lactate.

In addition, some calcium supplements are combined with vitamins and other minerals. For instance, some calcium supplements may also contain vitamin D or magnesium. Check the ingredient list to see which form of calcium your calcium supplement is and what other nutrients it may contain. This information is important if you have any health or dietary concerns.

However, calcium supplements interact with some medicines when they are taken at the same time. When this happens, it can often increase or decrease the amount of medicine that your body absorbs. Sometimes, it works the other way around and the medicine changes how much calcium your body absorbs. So, either the calcium supplement or the medicine does not work very well. Here is one example of an interaction when taking a calcium supplement at the same time as a certain antibiotic, leading to ineffective treatment of a serious infection.

A consumer with diabetes received prescriptions for two antibiotics to treat a serious foot infection. One of these antibiotics was ciprofloxacin (Cipro) which belongs to a class of drugs called quinolone antibiotics. When ciprofloxacin and a calcium supplement are taken at the same time, the ciprofloxacin is not absorbed properly, this makes it unable to fight the infection effectively. When the consumer filled the antibiotic prescriptions at his local pharmacy, the pharmacist did not tell him to take the ciprofloxacin at least 2 hours before or 6 hours after taking his calcium supplement to avoid an interaction. Also, the pharmacy label on his medicine vial did not warn him to do this. Because he took his ciprofloxacin at the same time as his calcium supplement, the antibiotic could not work and his foot infection was not properly treated.

Calcium supplements are usually safe to take, but you need to consider what else you are taking—and it is not just ciprofloxacin that is a problem. This is not a complete list, but the following are just a few examples of the types of medicines that may interact with calcium supplements and should be taken a few hours apart:

Antibiotics: Calcium supplements can decrease the absorption of certain antibiotics, including tetracycline, ciprofloxacin, levofloxacin, and norfloxacin. Taking these antibiotics at least 2 hours before or 6 hours after the calcium supplement should help, but again, speak with your healthcare provider for specific instructions.

Osteoporosis medicines: Taking calcium supplements and bisphosphonates (used to treat osteoporosis [weak bones]) at the same time may decrease the absorption of the osteoporosis medicines. Bisphosphonates include alendronate (Fosamax, Binosto), ibandronate (Boniva), and risedronate (Actonel, Atelvia). Calcium supplements should be taken at least 30 to 60 minutes after the osteoporosis medicine.

Anti-seizure medicines: Medicines used to control seizures, such as phenytoin (Dilantin), carbamazepine (Carbatrol, Equetro, Tegretol, Epitol), phenobarbital, and primidone (Mysoline), may lower your calcium levels or the levels of anti-seizure medicines. They need to be taken at least 2 hours before or after calcium supplements.

Here’s what you can do: It is very important to talk to your pharmacist or another healthcare provider about taking calcium supplements (or any other dietary supplement), especially if you have any health conditions or are taking other medicines, including over-the-counter (OTC) medicines. Also consider the following tips to avoid interactions between dietary supplements and medicines:

• Keep your medicine list updated with all prescription and OTC medicines, dietary supplements, and herbal products. Be sure to include any vitamins and minerals that you take, such as calcium. Show this list to your pharmacist and every other healthcare provider, especially before starting a new medicine.

• Talk to your pharmacist about any new medicines you start. Ask if there are any foods, drinks, dietary supplements, herbals, or other products that you should avoid.

• When buying a dietary supplement, including calcium supplements, always ask the pharmacist whether it is safe to take with your current medicines.

• Really, this is so important that it bears repeating: Talk to your pharmacist or another healthcare provider about any dietary supplements you take.

Keep in mind: Most studies suggest that multivitamins won’t make you live longer, slow cognitive decline or lower your chances of disease, such as heart disease, cancer or diabetes. In fact, it’s illegal for companies to make claims that supplements will treat, diagnose, prevent or cure diseases.


Dr. Oche Otorkpa PG Cert, MPH, PhD

Dr. Oche is a seasoned Public Health specialist who holds a post graduate certificate in Pharmacology and Therapeutics, an MPH, and a PhD both from Texila American University. He is a member of the International Society of Substance Use Professionals and a Fellow of the Royal Society for Public Health in the UK. He authored two books: "The Unseen Terrorist," published by AuthorHouse UK, and "The Night Before I Killed Addiction."
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