Calcium
The small intestine needs vitamin D to absorb calcium; 99% of body calcium is in bones and teeth.
Full ranking Dose tool Products (6,913)
Key facts
Sources: https://ods.od.nih.gov/factsheets/Calcium-HealthProfessional/ · FDA DV 1300 mg (https://www.fda.gov/food/nutrition-facts-label/daily-value-nutrition-and-supplement-facts-labels); pre-2016 DV [1000] (https://www.federalregister.gov/documents/2016/05/27/2016-11867/food-labeling-revision-of-the-nutrition-and-supplement-facts-labels); adult UL 2500 mg
How it works: How does calcium get into bone?
- Calcium is absorbed in the small intestine; active absorption needs vitamin D. Absorption is highest at single doses of 500 mg or less.
- About 1% of calcium is in blood and cells, used for muscle contraction, nerve signalling and blood vessel function.
- The other 99% is stored in bones and teeth and is constantly exchanged with the blood.
Schematic only; positions and scale are not anatomical.
Sources: NIH ODS: Calcium Fact Sheet for Health Professionals
Daily dose across products (mg/day)
Label data from official national databases and brand websites, as declared; not lab-verified.
Common forms
| Form | Products | Median | P5–P95 | Elemental fraction |
|---|---|---|---|---|
| Calcium carbonate | 1888 | 200 mg | 20 – 1,000 | 40.0% [source] |
| Calcium citrate | 1026 | 145 mg | 17 – 600 | 21.1% [source] |
| Calcium phosphate | 746 | 100 mg | 22 – 500 | — |
| Calcium malate | 170 | 150 mg | 25 – 650 | — |
| Calcium lactate | 148 | 86.8 mg | 14.5 – 520 | 13.0% [source] |
| Calcium gluconate | 122 | 117 mg | 3.58 – 650 | 8.9% [source] |
| Calcium bisglycinate | 84 | 50 mg | 2 – 250 | — |
| Calcium hydroxyapatite | 53 | 220 mg | 3 – 1,000 | — |
| Calcium coral | 42 | 300 mg | 50 – 1,000 | — |
| Calcium algae | 38 | 75 mg | 25 – 1,000 | — |
Common questions
What is the Daily Value for Calcium?
The US FDA Daily Value for adults and children aged 4 and over is 1,300 mg. It is a labelling reference, not a personal recommendation. [source]
Is there an upper limit for Calcium?
The adult Tolerable Upper Intake Level (UL) is 2,500 mg per day. Going above it long term raises the risk of adverse effects. See the linked source. [source]
How much Calcium do products usually contain per day?
As of 2026-11-01, 6,913 products list a comparable daily dose (7,555 dose records; one product can have several). The median is 100 mg per day, and 90% of records fall between 11.9 and 667 mg. Figures come from labels and are not lab-tested. [source]
How does calcium get into bone?
The small intestine needs vitamin D to absorb calcium; 99% of body calcium is in bones and teeth. Adult UL: 2,500 mg per day for ages 19–50, 2,000 mg per day from age 51. [source]
What are the side effects of Calcium?
Some people get gas, bloating or constipation from calcium supplements. Calcium carbonate causes these more often than calcium citrate, especially in older adults with less stomach acid. Switching forms, taking smaller doses more often, or taking it with meals can help. (Source: NIH ODS) [source]
What happens if you take too much Calcium?
The adult UL is 2,500 mg a day for ages 19–50 and 2,000 mg for 51+, from food and supplements combined. It is based on evidence linking supplemental calcium to kidney stones, though later reviews did not confirm the link. Some studies suggest calcium supplements may raise cardiovascular risk; findings are mixed. (Source: NIH ODS) [source]
Is Calcium safe during pregnancy and breastfeeding?
The RDA in pregnancy and breastfeeding is 1,300 mg (ages 14–18) and 1,000 mg (19–50), the same as for other women that age. The UL is 3,000 and 2,500 mg. In pregnant women with low calcium intake, supplements may lower the risk of preeclampsia. (Source: NIH ODS) [source]
Does Calcium interact with medications or other supplements?
Take dolutegravir 2 hours before or 6 hours after calcium supplements. Keep levothyroxine and calcium carbonate 4 hours apart. Take quinolone antibiotics 2 hours before or after calcium. Long-term lithium can cause high blood calcium, and calcium supplements may add to that risk. (Source: NIH ODS) [source]
How and when should you take Calcium?
Take calcium carbonate with a meal, especially if you have low stomach acid; calcium citrate depends less on stomach acid and can be taken without food. In general, calcium is absorbed better with food. Absorption is highest at 500 mg or less per dose, so split larger amounts. (Source: NIH ODS) [source]
Top ranked
| Rank | Brand | Product | Per day | Score |
|---|---|---|---|---|
| 1 | Bayer | Alka-Seltzer Extra Strength Heartburn Relief Chews Assorted Fruit | 1,502 mg | 94.4 |
| 1 | The Vitamin Shoppe | Calcium Citrate 300 mg | 1,200 mg | 94.4 |
| 3 | Nature's Way | Calcium Citrate | 1,000 mg | 84.2 |
| 3 | Solgar | Chelated Calcium | 1,000 mg | 84.2 |
| 5 | Allergy Research Group | Calcium Pyruvate | 840 mg | 78.7 |