6 Medications That Can Cause Hypercalcemia (High Calcium Levels)

While calcium is most commonly known for keeping your bones and teeth strong, it actually has many roles in the body. These include helping your muscles, blood vessels, and nervous system function well. But if calcium levels become too high (hypercalcemia), it can lead to muscle weakness, confusion, and even dangerous changes to your heart rate and blood pressure.

High calcium levels are typically caused by cancer or parathyroid issues. But medications can sometimes be to blame. Here, we’ll review six medications that can also cause hypercalcemia.

1. Lithium

Lithium (Lithobid) is a medication that treats bipolar disorder. Lithium can affect several different electrolyte levels in your body, including calcium.

It isn’t clear exactly how lithium increases calcium levels. But it seems that lithium makes the body believe that calcium levels are lower than they actually are. In turn, this causes the body to release more calcium into the bloodstream, which raises calcium levels higher than they should be.

Lithium is a medication with a narrow therapeutic index. This means there’s a small window between a safe, effective dose and an ineffective or toxic dose. So your prescriber will perform regular blood tests to make sure your lithium levels stay within a safe range. They may also check your other levels, including calcium, to watch for any changes. That’s why it’s important to keep up with your monitoring appointments while you’re taking lithium. And be sure to let your prescriber know if you notice any changes in how you’re feeling during treatment.

2. Thiazide diuretics

Thiazide diuretics (water pills) remove excess fluid from the body. Examples include hydrochlorothiazide (Microzide) and chlorthalidone (Thalitone).

Thiazide diuretics can raise calcium levels by preventing calcium from being removed from the body in your urine. Your prescriber will likely keep an eye on your electrolyte levels during treatment to watch for this side effect. But let them know if you notice symptoms such as excessive thirst, weakness, or a slower-than-usual heart rate.

3. Tamoxifen

Tamoxifen (Soltamox) is a medication that treats and prevents hormone-positive breast cancer. In people with cancer that has spread to the bones, tamoxifen may cause what’s known as a disease flare. Symptoms can include increased bone pain. This response is typically temporary, but it may lead to high calcium levels in some people.

In some cases, hypercalcemia with tamoxifen will resolve on its own. In others, you may need to stop taking tamoxifen for a short time, or your prescriber may add another medication to lower your calcium levels.

EXPERT PICKS: WHAT TO READ NEXT

• Hypercalcemia 101: Read more about the causes, symptoms, and treatments for high calcium levels in the body.

• Calcium overdose: Learn how much calcium is too much, along with what symptoms to watch for.

• Signs of low calcium: Here are the signs and symptoms of hypocalcemia (low calcium levels) and what to do about it.

4. Antacids that contain calcium

Calcium carbonate is a common ingredient in over-the-counter (OTC) antacids, such as Tums and Rolaids. But if you take them regularly, these antacids can cause high calcium levels. This side effect is often referred to as antacid-alkalai (or milk-alkalai) syndrome.

Hypercalcemia from antacids is more likely if you:

• Take them on a regular basis

• Are taking medications that can affect your kidneys, such as a thiazide diuretic or angiotensin-converting enzyme (ACE) inhibitor

Keep in mind that hypercalcemia from antacids isn’t likely if you only take them once in a while for heartburn. But you shouldn’t take an antacid as a daily calcium supplement unless your prescriber tells you to. In most cases, they’ll recommend a calcium supplement that’s less likely to cause this side effect — especially if you have a higher risk of developing it.

5. Vitamin D supplements

Vitamin D helps your body absorb calcium from your diet. But if you take too much vitamin D, it can in turn increase your calcium levels, leading to hypercalcemia.

Hypercalcemia isn’t common if you’re taking less than 10,000 international units (IUs) of vitamin D per day. But it can happen at lower doses for some people. It’s best to only take a vitamin D supplement if your prescriber recommends it. And be sure to follow the recommended dosage.

The risk for hypercalcemia also applies to calcium supplements, both on their own or with added vitamin D. It’s best to only take calcium and vitamin D supplements if your prescriber recommends it.

6. Forteo and Tymlos

Teriparatide (Forteo) and abaloparatide (Tymlos) are injectable medications that treat osteoporosis. They contain a lab-made version of parathyroid hormone (PTH). PTH helps regulate calcium levels in the body. So both medications can raise calcium levels after you inject them. Because of this, teriparatide and abaloparatide aren’t recommended if you already have high calcium levels or are living with a health condition that’s affected by high calcium levels, such as kidney stones.

In most cases, hypercalcemia caused by these osteoporosis medications is temporary and doesn’t cause any serious issues. But in rare cases, it can cause more serious problems. Your prescriber will likely check your calcium levels during the first few months of teriparatide or abaloparatide treatment to keep an eye out for this side effect.

What else can cause high calcium levels?

Hypercalcemia can have many causes other than the medications you’re taking. These include:

• Excess PTH levels due to an enlarged PTH gland or tumor

• Cancer

• Dehydration

• Overactive thyroid

• Chronic kidney disease

• Immobility for a long period of time (more likely with children)

• Tuberculosis

• Sarcoidosis

• Paget disease

Symptoms of high calcium levels

You may not have noticeable symptoms unless your calcium levels are severely high.

Normal calcium levels range from 8.8 mg/dL to 10.4 mg/dL. High calcium levels under 12 mg/dL typically don’t cause symptoms. But you may have constipation or feel more tired than usual. High calcium levels above 12 mg/dL can cause symptoms such as:

• Confusion or mood changes

• Muscle weakness

• Increased thirst

• Frequent urination (peeing)

• Kidney stones

• Nausea or vomiting

• Dehydration

• Heart block

• Slow or irregular heart rate

• Coma

If you suspect that you may have a calcium imbalance, talk with your healthcare team. They can advise you on next steps, such as getting a calcium blood test.  If you do have high calcium levels, they’ll help determine the cause and develop a treatment plan for you to help lower them.

Frequently asked questions

Why trust our experts?

Written by:

Stacia Woodcock, PharmD

Stacia Woodcock, PharmD, is a pharmacy editor for GoodRx. She earned her Doctor of Pharmacy degree from the University of Kentucky and is licensed in New York and Massachusetts.

Reviewed by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

Our editorial standards

Meet our experts