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ingestible · for bone health & osteoporosis prevention

Calcium + Vitamin D

Reviewed by the Nimbera editorial team · Last updated May 2026

Weaver 2016 Osteoporosis International (PMID 26510847) - meta-analysis of 8 RCTs (30,970 participants) found combined calcium + vitamin D supplementation reduced total fracture risk by 15% and hip fracture risk by 30% compared to placebo.$10-$25/month depending on brand and form

How to use

Calcium: 1,000-1,200 mg/day total (dietary + supplement combined). Supplement with 500-600 mg doses taken with meals for best absorption - do not take more than 600 mg at one time. Vitamin D3: 1,000-2,000 IU/day; aim for serum 25(OH)D of 30-50 ng/mL. Have your vitamin D level tested before supplementing at high doses.

How it works

Calcium is the primary structural mineral in bone hydroxyapatite. The skeleton contains 99% of the body's calcium and acts as a reservoir; when dietary intake is low, parathyroid hormone draws calcium from bone to maintain blood levels, accelerating bone loss. Vitamin D3 is converted to its active form (calcitriol) which upregulates intestinal calcium-absorption proteins, roughly doubling the fraction of dietary calcium absorbed. Together they reduce compensatory bone resorption driven by secondary hyperparathyroidism.

Where to buy

Nature Made Calcium 600 mg + D3, Citracal Petites (calcium citrate - better absorbed without food), Thorne Calcium-D, and Garden of Life Vitamin D3 5000 IU are quality options. Calcium citrate is preferred over carbonate for those over 50 or with low stomach acid.

Typical cost: $10-$25/month depending on brand and form

Safety notes

Calcium supplements interact with levothyroxine (thyroid hormone) and bisphosphonates (alendronate, risedronate) - take at least 2 hours apart. Calcium carbonate requires stomach acid and should be taken with meals; calcium citrate can be taken any time. Do not exceed 2,500 mg calcium/day total - excess intake has been associated with kidney stones. Vitamin D toxicity (hypercalcemia) is rare but possible above 10,000 IU/day long-term. Calcium + vitamin D do not replace DEXA screening or prescribed osteoporosis treatment.

Drug & supplement interactions

  • Always tell your doctor or pharmacist about any supplements you take.
  • Interactions can occur with prescription medications, blood thinners, and immunosuppressants.
  • Herbal remedies can affect how the body absorbs or metabolises drugs.
  • Check drugs.com interactions checker before starting.

Clinical source

Weaver 2016 - Osteoporosis International (PMID 26510847)

This information is compiled from primary clinical literature and is for informational purposes only. It is not a substitute for professional medical advice. Read our full disclaimer.