Calcitonin: What it is and how people use it

Calcitonin is a hormone medicine that lowers blood calcium and slows bone breakdown. You’ll most often see it as a nasal spray or an injectable shot. Doctors prescribe it for high blood calcium (hypercalcemia), Paget’s disease of bone, and sometimes for osteoporosis when other drugs aren’t suitable.

How calcitonin works and common uses

Calcitonin tells bone cells to slow the breakdown of bone, which helps keep calcium in bones instead of the bloodstream. That makes it useful when calcium levels are dangerously high. For osteoporosis, it’s a second-line option — helpful if you can’t take bisphosphonates or have severe bone pain from vertebral fractures. The brand form most commonly used is salmon calcitonin, since it’s more stable and works well in humans.

Forms you’ll see: a nasal spray (usually once daily) and subcutaneous or intramuscular injections (daily or every other day depending on the situation). The nasal spray is often chosen for long-term use because it’s easier to use at home. The injection is common in hospital settings, especially for severe hypercalcemia.

Side effects, dosing basics, and safety tips

Common side effects are mild: nasal irritation, runny nose, nausea, flushing, and occasional headache. Injection can cause redness at the site, nausea, or dizziness. Severe allergic reactions are rare but possible — stop the medicine and get medical help if you have trouble breathing, swelling, or hives.

Dosing varies by condition. A typical nasal dose for osteoporosis might be one spray per day (follow your product instructions). Injections are dosed by a clinician — do not guess. If you miss a dose of the nasal spray, skip it and use the next day; don’t double up.

Practical tips: store the nasal spray at room temperature away from moisture; keep injections refrigerated until use if the label says so. Check labels and talk to your pharmacist about storage. Tell your doctor about other medicines you take — especially diuretics, lithium, or strong calcium supplements — because calcitonin affects calcium balance and can interact.

Who should avoid it? Don’t use calcitonin if you’ve had an allergy to salmon or calcitonin products. Use caution in pregnant or breastfeeding people — your doctor will weigh risks and benefits. Also, if you have low blood calcium (hypocalcemia), calcitonin may make it worse.

Want alternatives? For most osteoporosis patients, doctors prefer bisphosphonates, denosumab, or anabolic agents because they reduce fracture risk more reliably. Calcitonin still has a place when those options aren’t tolerated or when bone pain from vertebral fracture needs short-term relief.

If you feel unusual symptoms after starting calcitonin, or your lab calcium levels change, contact your provider. Small changes can be handled easily; serious shifts need prompt care. Ask your clinician about how long you should stay on calcitonin and whether bone density scans or blood tests are needed while you’re on it.