Home Ingredients GivoCal® (Calcium Glycerophosphate — Isaltis)
Bone Health

GivoCal® (Calcium Glycerophosphate — Isaltis)

Evidence Level
Moderate
2 Clinical Trials
3 Documented Benefits
3/5 Evidence Score

GivoCal is a branded calcium glycerophosphate made by the mineral-salt producer Isaltis for supplements and foods. Calcium glycerophosphate is a water-soluble salt that supplies both calcium and phosphorus; by its chemical formula it is about 19% calcium and 15% phosphorus by weight in its dry form. Calcium is the main mineral of bone, where it combines with phosphate as hydroxyapatite. Trials of calcium in general show that supplements raise bone mineral density by a small amount, about 0.7% to 1.8%, and that the gain does not keep growing over time. No published trial has tested GivoCal on bone, and calcium glycerophosphate itself has bone data only from a small trial in preterm infants given fortified breast milk, so its bone benefit for adults is borrowed from studies of other calcium forms. No published human study has compared its absorption with other calcium forms.

Studied Dose No dose of GivoCal itself has been studied. Calcium trials used a range of doses, and absorption is highest when 500 mg of elemental calcium or less is taken at a time.
Active Compound Calcium glycerophosphate (C3H7CaO6P), supplying calcium and phosphorus.

Benefits

Bone mineral density

Calcium is the main mineral in bone. Pooled data from 51 trials of calcium supplements in people over 50 show bone density rising by 0.7% to 1.8%, a small gain that did not grow over time and is unlikely to cut fracture risk much. None of these trials tested GivoCal.

Supported by Trial 1, Trial 2

Calcium and vitamin D in postmenopausal women

Pooled trials of calcium with vitamin D in postmenopausal women found higher bone density at several sites and fewer hip fractures. In subgroups, the gains in total and spine bone density were clear only for fortified dairy foods, not for combined supplements. GivoCal, which has no vitamin D, was not tested.

Supported by Trial 2, Trial 1

Muscle and nerve function

A small pool of calcium in the blood and tissues is needed for muscle contraction, nerve signaling, blood clotting and hormone release. The body keeps blood calcium in a tight range, drawing on bone when intake is low.

Supported by Trial 1, Trial 2

Mechanism of action

1

Bone mineralization

More than 99% of body calcium is in bones and teeth as hydroxyapatite, a crystal of calcium and phosphate.

2

Calcium balance

Bone acts as the body's calcium reserve; it is constantly broken down and rebuilt, and the body draws calcium from it when intake is too low to keep blood levels steady.

3

Calcium plus phosphorus source

Calcium glycerophosphate releases both calcium and glycerophosphate, so it also adds phosphorus, a mineral most diets already supply in ample amounts.

Clinical trials

1
Calcium Intake and Bone Mineral Density: Meta-Analysis
PubMed

Random-effects meta-analysis of randomized controlled trials of dietary calcium or calcium supplements, with or without vitamin D. (Tai et al. 2015, BMJ)

59 trials in people over 50: 51 trials of supplements (12,257 people) and 15 of dietary calcium (1,533 people).

Calcium supplements raised bone mineral density by 0.7% to 1.8% at five skeletal sites, with no further gain after the first year. The authors judged the increase unlikely to lead to a clinically important reduction in fractures. None of the trials tested GivoCal.

2
Calcium and Vitamin D in Postmenopausal Women: Meta-Analysis
PubMed

Systematic review and meta-analysis of randomized controlled trials of combined calcium and vitamin D. (Liu et al. 2020, Food Funct)

Postmenopausal women across the included trials.

Combined calcium and vitamin D raised total, spine, arm and hip-neck bone density and lowered hip fracture risk (RR 0.86). In subgroups, total and spine bone density gains were significant only for fortified dairy foods, not for combined supplements.

Side effects and drug interactions

Common Potential side effects

Gas, bloating and constipation can occur with calcium supplements.
Absorption is highest when 500 mg of elemental calcium or less is taken at a time.
Higher supplemental calcium intakes might raise kidney stone risk.
Some studies link calcium supplements to higher cardiovascular risk while others do not; the adult upper limit is 2,000 to 2,500 mg a day from all sources, depending on age.

Important Drug interactions

Quinolone antibiotics (such as ciprofloxacin): calcium reduces their absorption; take the antibiotic 2 hours before or after.
Levothyroxine: calcium supplements can reduce its absorption; the drug label advises a 4-hour gap from calcium carbonate.
Dolutegravir: calcium can substantially lower its blood levels; follow the label spacing.
Lithium: long-term use can raise blood calcium, and adding calcium supplements could increase that risk.

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Frequently asked questions about GivoCal® (Calcium Glycerophosphate — Isaltis)

What is GivoCal?

GivoCal is Isaltis's brand of calcium glycerophosphate, a water-soluble salt that supplies calcium and phosphorus for supplements and foods.

Has GivoCal been tested in people?

No published trial has tested GivoCal for bone. Calcium glycerophosphate has been studied for bone only in a small trial in preterm infants given fortified breast milk. Its expected bone effect in adults comes from trials of calcium in general, which show small gains in bone density.

How should calcium be taken?

Absorption is best in doses of 500 mg of elemental calcium or less at a time, so larger daily amounts are usually split. Count calcium from food toward your total.

What is GivoCal used for?

GivoCal is researched primarily for Bone Health. Calcium is the main mineral in bone. Pooled data from 51 trials of calcium supplements in people over 50 show bone density rising by 0.7% to 1.8%, a small gain that did not grow over time and is unlikely to cut fracture risk much.

What is the recommended dosage of GivoCal?

No dose of GivoCal itself has been studied. Calcium trials used a range of doses, and absorption is highest when 500 mg of elemental calcium or less is taken at a time. Always follow the product label and check with a healthcare provider for personal advice.

Is GivoCal safe, and does it have side effects?

Side effects and cautions reported for GivoCal include: Gas, bloating and constipation can occur with calcium supplements. Absorption is highest when 500 mg of elemental calcium or less is taken at a time. It may also interact with some medications. GivoCal is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does GivoCal interact with any medications?

Possible interactions include: Quinolone antibiotics (such as ciprofloxacin): calcium reduces their absorption; take the antibiotic 2 hours before or after. Levothyroxine: calcium supplements can reduce its absorption; the drug label advises a 4-hour gap from calcium carbonate. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for GivoCal?

NutraSmarts rates the evidence for GivoCal as Moderate (3 out of 5). It is backed by 2 study summaries and 7 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(7 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Tai V, Leung W, Grey A, Reid IR, Bolland MJ. Calcium intake and bone mineral density: systematic review and meta-analysis. BMJ. 2015;351:h4183. doi: 10.1136/bmj.h4183.PubMedUsed to support: Meta-analysis of 59 randomized trials in people over 50: calcium supplements (51 trials, 12,257 people) raised bone mineral density by 0.7% to 1.8% at five sites, with no progressive gain; dietary calcium had similar effects; the authors judged these gains unlikely to cut fractures meaningfully.
  2. Bolland MJ, Leung W, Tai V, Bastin S, Gamble GD, Grey A, Reid IR. Calcium intake and risk of fracture: systematic review. BMJ. 2015;351:h4580. doi: 10.1136/bmj.h4580.PubMedUsed to support: Systematic review: in 26 randomized trials calcium supplements reduced total fracture (RR 0.89) and vertebral fracture risk, but not hip or forearm fracture; trials at lowest risk of bias showed no effect, and the authors called the evidence weak and inconsistent.
  3. Liu C, Kuang X, Li K, Guo X, Deng Q, Li D. Effects of combined calcium and vitamin D supplementation on osteoporosis in postmenopausal women: a systematic review and meta-analysis of randomized controlled trials. Food Funct. 2020;11(12):10817-10827. doi: 10.1039/d0fo00787k.PubMedUsed to support: Meta-analysis of randomized trials in postmenopausal women: combined calcium and vitamin D raised total, spine, arm and femoral neck bone density and lowered hip fracture risk (RR 0.864); in subgroups only fortified dairy foods, not combined supplements, significantly raised total and spine bone density.
  4. Office of Dietary Supplements, National Institutes of Health. Calcium: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. 2026;Online fact sheet, updated June 22, 2026..SourceUsed to support: Not PubMed-indexed. More than 99% of body calcium is in bones and teeth as hydroxyapatite; the circulating pool supports muscle function, nerve transmission, blood clotting and hormone secretion; absorption is highest at 500 mg or less per dose; gas, bloating and constipation; possible kidney stone and cardiovascular concerns; adult UL 2,000 to 2,500 mg; interactions with quinolone antibiotics, levothyroxine, dolutegravir and lithium.
  5. Isaltis. GIVOCAL (Calcium Glycerophosphate): calcium glycerophosphate for nutrition. Isaltis product listing. 2026;Manufacturer product page..SourceUsed to support: Not PubMed-indexed. Manufacturer listing identifying GIVOCAL as Isaltis's calcium glycerophosphate for nutrition, described by the maker as highly bioavailable (a marketing claim, not a human trial).
  6. National Center for Biotechnology Information. Calcium glycerophosphate (CID 62820). PubChem. 2026;Compound record CID 62820..SourceUsed to support: Not PubMed-indexed. Gives the formula C3H7CaO6P and molecular weight 210.14, from which the dry salt is about 19% calcium and 15% phosphorus by weight.
  7. Wauben IP, Atkinson SA, Grad TL, Shah JK, Paes B. Moderate nutrient supplementation of mother's milk for preterm infants supports adequate bone mass and short-term growth: a randomized, controlled trial. Am J Clin Nutr. 1998;67(3):465-72. doi: 10.1093/ajcn/67.3.465.PubMedUsed to support: Randomized trial in 25 preterm infants fed mother's milk: calcium and phosphorus added as calcium glycerophosphate gave adequate whole-body bone mineral content, with no bone advantage from a multinutrient fortifier, though weight and length gain were lower than with preterm formula. Not a study of GivoCal or of adults.