8 Calcium Citrate Interactions to Know About
Key takeaways:
Calcium citrate (Citracal) can bind to certain medications and reduce their absorption. This includes thyroid hormone medications, some antibiotics, and dolutegravir. Calcium citrate can also interact with iron supplements and bisphosphonates.
You can avoid some calcium citrate interactions by taking it 2 to 4 hours before or after other medications. Talk to your prescriber before taking calcium citrate with your current medications. They can provide guidance for how to take it safely.
Lithium and thiazide diuretics can increase your calcium levels. Taking them along with calcium citrate can cause your calcium levels to become too high. You shouldn’t take calcium citrate with these medications unless your prescriber recommends it.
Table of contents
Calcium citrate (Citracal) is a type of calcium supplement. Your body needs calcium to keep your bones, muscles, and nerves healthy. You may need a calcium citrate supplement if your blood calcium levels are low or you have low bone density.
But you shouldn’t take a calcium citrate supplement unless a healthcare professional recommends it. That’s because there are side effects and drug interactions to consider, which are easy things to overlook with over-the-counter (OTC) supplements. Let’s take a look at eight calcium citrate interactions to be aware of before taking it.
1. Levothyroxine and other thyroid hormone medications
Levothyroxine (Synthroid, Levoxyl) is a thyroid hormone medication that’s used to treat hypothyroidism (low thyroid hormone levels). Other thyroid hormone medications include liothyronine (Cytomel) and desiccated thyroid (Armour Thyroid, NP Thyroid).
Search and compare options
Calcium supplements can interfere with the absorption of thyroid hormone medications. One small study found taking these two together reduced thyroid hormone levels almost 25%. If you don’t have enough thyroid hormone, symptoms of hypothyroidism may occur. This can include low energy, dry skin, and hair loss.
To help avoid this, you should take calcium citrate and thyroid hormone medication at least 4 hours apart.
2. Lithium
Lithium (Lithobid) is a medication that treats bipolar disorder. Lithium can raise your calcium levels. If you also take calcium citrate, this combination may raise your calcium levels too much (hypercalcemia).
Signs and symptoms of hypercalcemia include:
Nausea
Constipation
Muscle weakness
Bone pain
Confusion
Fatigue
Feeling thirsty
Peeing more often
If you take lithium, talk with your prescriber before taking calcium citrate. They can check your calcium levels and determine if it’s a safe and necessary supplement for you.
How much calcium is too much? Learn how much calcium you should consume daily and the risks of taking too much.
Calcium carbonate vs. calcium citrate: Both of these supplements can increase calcium levels, but there are some important differences between the two.
Calcium citrate side effects: Here are some common and rare side effects to be aware of if you’re taking calcium citrate.
3. Thiazide diuretics
Thiazide diuretics (or water pills) help remove excess fluid from the body. But they may also increase how much calcium your body holds onto. Hydrochlorothiazide (Microzide) and chlorthalidone are the diuretics included in this drug class.
If you take a thiazide diuretic along with calcium citrate, it’s possible your calcium levels may become too high. As mentioned, high calcium levels can cause unpleasant symptoms and may even be dangerous in severe cases.
Be sure to talk with your healthcare team before taking calcium citrate along with a thiazide diuretic to make sure it’s appropriate for you.
Read more like this
Explore these related articles, suggested for readers like you.
4. Fluoroquinolone antibiotics
Fluoroquinolone antibiotics treat bacterial infections. They’re typically reserved for more serious infections or when other antibiotics aren’t an option. This is because they carry some serious risks. Common fluoroquinolones include:
Ciprofloxacin (Cipro)
Levofloxacin
Moxifloxacin (Avelox)
Calcium citrate can significantly reduce the absorption of fluoroquinolones. This can make them less effective at treating your infection. Let your prescriber know if you’re taking calcium citrate and need a fluoroquinolone antibiotic. They may pause your calcium supplement until your course of antibiotics is finished. Or they may have you take calcium citrate at least 2 hours before or after your antibiotic.
5. Tetracycline antibiotics
Tetracycline antibiotics also treat bacterial infections. Some are also prescribed for daily use to treat and prevent acne. Common tetracycline antibiotics include doxycycline (Doryx), minocycline (Minocin), and tetracycline.
Calcium can bind to tetracycline antibiotics. This makes it harder for your body to absorb them properly, which results in lower antibiotic levels in your body. As with fluoroquinolones, this interaction can leave your infection untreated.
Make sure your prescriber is aware you’re taking a calcium citrate supplement for starting an antibiotic. They’ll let you know if you should stop taking it or if you need to separate it from your antibiotic. In most cases, you should take a tetracycline antibiotic at least 2 hours before or after taking calcium citrate.
6. Alendronate and other bisphosphonates
Bisphosphonates are medications that can help you maintain your bone density. They’re typically prescribed for osteoporosis. Common bisphosphonates include alendronate (Fosamax), risedronate (Actonel), and ibandronate (Boniva).
Calcium citrate can bind to bisphosphonate medications and decrease their absorption. When this happens, bisphosphonates might not work well enough to protect your bones. This could increase your risk of bone fractures.
In some cases, it's recommended that you take a calcium supplement if you’re prescribed a bisphosphonate. But you shouldn’t take them at the same time. Your prescriber may suggest skipping calcium on the day you take your bisphosphonate. But in general, separating the two medications by at least 2 hours is fine. Your prescriber can give you specific directions based on your personal history.
7. Iron supplements
Iron supplements are often prescribed to prevent or treat anemia (decreased red blood cells) caused by low iron levels. Iron supplements are available in both OTC and prescription forms. They may go by different names, such as ferrous sulfate, ferrous gluconate, or ferric citrate.
Calcium citrate may make it harder for the body to absorb iron. This could prevent your iron supplement from working properly. It’s unclear how serious of a risk this interaction is, but most experts recommend separating the two medications by at least 2 hours to be on the safe side.
8. Dolutegravir
Dolutegravir (Tivicay, Dovato, Juluca) is an antiviral HIV medication. Calcium citrate can bind to dolutegravir and prevent your body from absorbing it. This could reduce your dolutegravir levels and make it less effective, which could in turn allow your viral load to go up.
You shouldn’t take calcium citrate with dolutegravir unless your prescriber recommends it. If you need both medications, take dolutegravir 2 hours before or 6 hours after calcium citrate.
The bottom line
Calcium citrate (Citracal) is a type of calcium supplement. It’s sold over the counter, but it can still interact with other medications. Calcium citrate can lower the levels of thyroid hormone medications, certain antibiotics, and dolutegravir if they’re taken at the same time. Calcium citrate can also lower the absorption of iron supplements and bisphosphonates. If you need to take calcium citrate with these medications, it’s best to separate the two by several hours. Your healthcare team can let you know how long is best based on your personal medical history.
Other calcium citrate interactions include thiazide diuretics and lithium. Your calcium levels may go too high if you take calcium citrate with either of these medications. So you shouldn’t take calcium citrate with them unless your prescriber recommends it.
Always talk with your healthcare team before taking calcium citrate to make sure it’s a safe and necessary supplement for you.
Why trust our experts?
References
Dietary Supplement Label Database. (n.d.). Calcium citrate search. National Institutes of Health.
Hooper, D. C. (2000). New uses for new and old quinolones and the challenge of resistance. Clinical Infectious Diseases.
Janknegt R. (1990). Drug interactions with quinolones. Journal of Antimicrobial Chemotherapy.
MedlinePlus. (2017). Tetracycline.
MedlinePlus. (2023). Taking iron supplements.
MedlinePlus. (2024). Hypercalcemia.
Middler, S., et al. (1973). Thiazide diuretics and calcium metabolism. Metabolism.
Office of Dietary Supplements. (2024). Iron: Fact sheet for health professionals. National Institutes of Health.
Song, I., et al. (2015). Pharmacokinetics of dolutegravir when administered with mineral supplements in healthy adult subjects. Journal of Clinical Pharmacology.
Wiesner, A., et al. (2021). Optimal dosing regimen of osteoporosis drugs in relation to food intake as the key for the enhancement of the treatment effectiveness—a concise literature review. Foods.
Zamfirescu, I., et al. (2015). Absorption of levothyroxine when coadministered with various calcium formulations. Thyroid.
