Short answer: Because these medicines can lower the calcium in your blood. The Prolia label says all patients should take 1,000 mg of calcium and at least 400 IU of vitamin D a day. The Reclast label recommends at least 1,200 mg of calcium and 800 to 1,000 IU of vitamin D a day if diet falls short. Fosamax, Actonel and Evenity labels ask for supplements when intake is not enough.
Bone medicines slow bone breakdown or speed bone building, and both pull on calcium. The Fosamax label (section 5.2) says low blood calcium must be corrected before starting, and that small decreases in blood calcium and phosphate may occur because of the medicine's effect on bone mineral. Prolia and Evenity carry hypocalcemia (low blood calcium) warnings (sections 5.1 and 5.3 respectively).
| Medicine | Section | What the label says |
|---|---|---|
| Prolia (denosumab) | 2.3 | All patients should receive calcium 1,000 mg daily and at least 400 IU vitamin D daily |
| Reclast (zoledronic acid), osteoporosis | 2.8 | Supplement if diet is short; an average of at least 1,200 mg calcium and 800 to 1,000 IU vitamin D daily is recommended |
| Reclast, Paget's disease | 2.8 | 1,500 mg calcium a day in divided doses and 800 IU vitamin D, particularly in the 2 weeks after the infusion |
| Fosamax (alendronate) | 2.7 | Supplemental calcium if intake is inadequate; some groups may need vitamin D (for example, over 70, nursing home-bound or chronically ill) |
| Actonel (risedronate) | 2.7 | Supplemental calcium and vitamin D if intake is inadequate |
| Evenity (romosozumab) | 2.2 | Adequately supplement calcium and vitamin D during treatment |
The amounts are what the labels set or recommend, not totals from supplements alone; food counts toward them. Your prescriber may set a different amount based on blood tests.
The Prolia Medication Guide says most people with low blood calcium have no symptoms, but some do, and lists spasms, twitches or cramps in the muscles, and numbness or tingling in the fingers, toes or around the mouth. It says to call the doctor right away for these. The Prolia label (section 17) tells prescribers to advise patients to seek prompt care for signs of hypocalcemia.
Prolia has a boxed warning about severe low calcium in people with advanced chronic kidney disease (eGFR below 30), including those on dialysis, where hospitalizations, life-threatening events and deaths have been reported. For them, the label asks for blood calcium checks weekly for the first month after each shot and monthly after that, and for treatment to be supervised by a provider experienced in kidney-related bone disease.
With Fosamax and other oral bisphosphonates, calcium cannot be taken at the same time: the label says calcium and other minerals interfere with absorption, so wait at least 30 minutes after the tablet. See how long after Fosamax you can take calcium. Injected and infused medicines such as Prolia, Reclast and Evenity have no such timing rule in their labels.
Dose Track can keep a daily calcium and vitamin D reminder alongside a weekly, monthly or 6-monthly bone medicine, and the calcium and vitamin D3 pages cover the supplements themselves.
Read more on Dose Track: Calcium supplements · Vitamin D3 · Prolia side effects · Reclast side effects · Evenity dosing schedule