The word “calcium” makes people think of bones, and here’s why: over 99% of the calcium present in an adult is found in the skeleton. In addition to bone structure, however, calcium is critical for many bodily functions including nerve transmission, blood clotting and coagulation, and muscle contraction.
Calcium is complicated. Calcium in the bloodstream is the measured calcium level seen on your lab results and it depends on the amount leaked from bones and movement across the intestines and kidneys. Your blood calcium level is controlled by changes in levels of two hormones: parathyroid hormone (PTH) and the active form of vitamin D called calcitriol.
A little complex, but here is the moral of the story. Your body needs just the right amount of calcium to function properly. Several medications are also known to mess with your calcium level, so here’s what you need to know.
High calcium levels in your bloodstream (hypercalcemia)
First off, what are the symptoms of hypercalcemia? If the elevated calcium in your bloodstream occurs suddenly and is severe, it may cause dramatic symptoms like confusion, sleepiness and even death. Hypercalcemia affects nearly every organ system in the body but the more common symptoms include weakness and confusion, frequent urination, kidney stones, constipation, nausea, and lack of appetite.
Here are some medications that cause high calcium levels:
- Lithium is used in the treatment of bipolar disorder and may raise your blood calcium level. Lithium stimulates the parathyroid hormone which tells the bones to release calcium into the bloodstream.
- Thiazide diuretics like hydrochlorothiazide (Microzide) and chlorthalidone are used to lower blood pressure and hypercalcemia is a well-known side effect. Hydrochlorothiazide and chlorthalidone may raise calcium by decreasing the amount of calcium that is released in the urine. This may also lead to calcium kidney stones.
- Calcium carbonate supplements can cause hypercalcemia. Many over-the-counter bone supplements and antacid relief tablets contain calcium carbonate. But how high is too high? Rule of thumb, don’t go above 6500 to 7500 mg per day.
- Vitamin D supplements like calcipotriol (Dovonex) may cause high calcium levels as well.
Low calcium levels in your bloodstream (hypocalcemia)
What are the signs of hypocalcemia? Think of hypocalcemia as causing neuromuscular irritability. Common complaints are numbness and tingling sensations around the mouth or in the fingers and toes. Muscle cramps, particularly in the back and lower extremities may progress to spasms in your hands and feet. Less common symptoms include wheezing, problems swallowing, irritability, depression, and fatigue.
Here are some medications that cause hypocalcemia:
- Osteoporosis medications called bisphosphonates may cause low blood calcium levels by reducing bone resorption. Less calcium is released into the bloodstream when bones are holding onto it. Hypocalcemia is more likely to occur with high doses of potent bisphosphonates, like zoledronic acid (Zometa) which is an intravenous infusion. Oral forms include ibandronate (Boniva) and alendronate (Fosamax) may also lead to hypocalcemia.
- Prolia is an injection to treat osteoporosis given once every 6 months which decreases bone resorption and may cause hypocalcemia.
- Sensipar is used in folks with chronic kidney disease to lower parathyroid hormone levels (PTH). Though not commonly used in people without kidney disease, it is known to lower blood calcium levels.
- Phenytoin (Dilantin) is a medication used to prevent seizures. Long-term use of Phenytoin may cause hypocalcemia. Cisplatin is a chemotherapy medication used for many advanced cancers including bladder, ovarian, testicular and esophageal among others, and it is known to cause hypocalcemia.