Calcium and vitamin D are important for bone health, and these nutrients also play an important role in muscle, nerves, and immune system health. Vitamin D helps the body absorb calcium, although you don’t have to take it in at the same time as calcium.
While calcium and vitamin D can be obtained through diet, people with certain conditions, such as weakened bones, may benefit from supplements.
The Relationship Between Calcium and Vitamin D
Calcium is a mineral found in bones and it plays a role throughout the body. Proper amounts of calcium in the blood and fluid between cells in the body are essential for muscle, heart, and nerve function. Vitamin D helps promote bone, muscle, and immune system health.
When levels of calcium in the blood are low, as in chronically not getting enough calcium from the diet, vitamin D and parathyroid hormone (PTH) signal the gut to absorb more calcium, the bones to release calcium, and the kidneys to reabsorb calcium so that it is not lost in the urine.
Too much calcium released from the bones can lead to bone weakness, known as osteoporosis. When calcium levels in the blood and fluids are too high, hormones signal the bones to take up more calcium and the kidneys to release calcium in the urine.
Mutual Benefits
Both calcium and vitamin D play important roles in keeping bones strong. Vitamin D helps the body absorb calcium. Without vitamin D, children develop rickets, a condition in which the bones are soft and malformed.
Low calcium in adults can lead to weakening of the bones and even fractures due to conditions known as osteomalacia and osteoporosis.
Absorption
Calcium is absorbed from the diet in the gastrointestinal tract with the help of vitamin D. Vitamin D can also come from the diet, especially through foods like fish and eggs. The body can also make some vitamin D with sunlight, which can vary depending on how far from the equator you live and how much sunlight you get.
Vitamin D is stored in the liver and fatty tissues as well as being manufactured in the skin. So long as you have an adequate amount through the diet or supplementation, it will help you absorb calcium whenever you take in calcium.
Supplementing Both at Once
Calcium and vitamin D may be taken together, and some supplements combine the two nutrients. Vitamin D helps the body absorb calcium.
Supplements containing calcium and vitamin D often contain about 500 to 600 milligrams (mg) of calcium. However, it’s important to note the amount of each nutrient in supplements and not exceed the recommended amounts. Talk with your healthcare provider about specific forms of calcium that may be suitable and appropriate doses.
Fracture Prevention
Studies have found that supplementing vitamin D and/or calcium did not reduce hip fractures in community-dwelling (defined as not living in a nursing home or other institution) older people. However, they may be beneficial in preventing fractures in people living in nursing homes.
The U.S. Preventative Services Task Force has the following recommendations for vitamin D and/or calcium supplementation for fracture prevention for community-dwelling people who do not have a history of osteoporotic fractures, increased risk for falls, diagnosis of osteoporosis, or vitamin D deficiency:
- No fracture-prevention benefit has been proven for community-dwelling men and pre-menopausal women.
- Balanced with risks of supplementation, evidence is insufficient for preventing fractures in community-dwelling postmenopausal women who take daily supplements containing more than 400 IU of vitamin D and more than 1,000 mg of calcium.
- For community-dwelling postmenopausal women, the USPSTF recommends against daily supplementation with 400 IU or less of vitamin D and 1,000 mg or less of calcium to prevent fractures.
Average Levels and Nutritional Needs
Calcium levels in adults are measured using blood tests, whereas bone density scans, known as dual-energy X-ray absorptiometry (DEXA) scans, provide information about bone density.
| Tests and Normal Ranges | |||
|---|---|---|---|
| Test | What It Is | What It Measures | Normal Range |
| Ionized Calcium | Blood test | Free calcium in the blood | 4.8 to 5.6 milligrams per deciliter (mg/dL) |
| Total Calcium | Blood test | Both free calcium and calcium attached to proteins in the blood | 8.5 to 10.5 mg/dL |
| DEXA scan | X-ray test | Bone density, using T score comparing density to a healthy adult | T score -1.0 or higher |
| 25-hydroxy Vitamin D | Blood test | Vitamin D levels in the blood | greater than 20 nanograms per milliliter (ng/mL) |
How Much Should You Take?
The recommended daily amounts for calcium vary by age and sex and are listed below. Keep in mind this includes all calcium combined from diet and supplements:
- Adults 19 to 50 years: 1,000 mg, regardless of pregnancy status
- Age 51 to 70: Male 1,000; female 1,200 mg
- Age over 70: 1,200 mg
The recommended daily intake of vitamin D varies by age. Most Americans do not get the recommended amounts of vitamin D:
- Age 19 to 70: 15 micrograms (mcg) or 600 international units (IU)
- Age 70 and over: 20 mcg (800 IU)
Healthcare providers may recommend higher doses than those listed for those who are found to be deficient in a nutrient or who have certain conditions.
For example, postmenopausal females (menstruation has ceased for at least a year) and people who do not consume dairy products are more at risk of calcium deficiency. Consult with your healthcare provider for advice.
A Note on Gender and Sex Terminology
Verywell Health acknowledges that sex and gender are related concepts, but they are not the same. To reflect our sources accurately, this article uses terms like “female,” “male,” “woman,” and “man” as the sources use them.
Potential Side Effects
Taking too much calcium or vitamin D supplements can have serious health consequences due to too much calcium in the blood. Some people may experience symptoms like gas, bloating, and constipation with calcium supplements. However, switching to a different supplement formulation or taking it at mealtimes may help.
Too much calcium supplements can cause the following problems:
- Gastrointestinal symptoms like nausea and constipation
- Abnormal heart rhythm (arrhythmia)
- Possible increased risk of kidney stones
- Possible increased risk of heart disease and cancer
Too much vitamin D can cause a condition known as hypervitaminosis D or vitamin D toxicity. This typically happens when people take very high doses of vitamin D, such as above 10,000 IU per day. This can lead to abnormally elevated calcium levels in the blood (hypercalcemia) and the following symptoms:
- Constipation
- Nausea, vomiting, and decreased appetite
- Dehydration and excessive thirst
- Frequent need to urinate and a large volume of urine
- Fatigue
- Confusion
- Muscle weakness
- Arrhythmias
Note that taking dietary supplements can also interfere with the absorption of certain medications. Before starting dietary supplements, talk with your healthcare provider.
Should I Take a Supplement or Eat Fortified Foods?
In general, people should aim to get nutrients through food; however, in some cases, supplementation is necessary. A healthcare provider may recommend calcium supplementation if you are postmenopausal, have osteoporosis, or do not get enough calcium in your diet, such as those who avoid dairy products.
Vitamin D supplementation is recommended for those with vitamin D deficiency. However, the exact cutoff of blood levels for the diagnosis is debated. In 2024, a panel of experts published guidance recommending vitamin D supplementation for the following groups:
- Age 1 to 18 years
- Age 75 years and older
- Pregnant individuals
- People with prediabetes at risk of progression to diabetes
Dietary Sources of Calcium
Calcium from dairy sources is generally better absorbed than that found in plant-based food. These foods are rich in calcium:
- Dairy products like milk, cheese, and yogurt.
- Sardines and salmon (with bones)
- Vegetables like broccoli, cabbage, and kale
- Fortified grains and cereals (nonfortified grains do not contain much calcium)
- Fortified tofu
- Fortified orange juice
Dietary Sources of Vitamin D
Vitamin D is not found naturally in as many foods, but fortified foods are available. You can get dietary vitamin D through the following foods:
- Fish, particularly the flesh of fatty fish like mackerel, salmon, trout, and tuna
- Beef liver
- Egg yolks
- Cheese
- Mushrooms
- Fortified foods, such as dairy milk and plant-based milk, orange juice, and some cereals
When to Contact a Healthcare Provider
In general, healthy adults should aim to get the nutrients they need from their diet rather than through dietary supplements; however, newer guidance recommends vitamin D supplementation for certain groups of people.
If you are concerned about low vitamin D levels or conditions like osteoporosis, visit a healthcare provider to determine whether blood testing and supplementation are needed.
If your healthcare provider has recommended supplements and you experience side effects, talk with them about your symptoms. They could be unrelated to the supplement. Timing supplements with food intake or switching to a different supplement could help.
Summary
Calcium and vitamin D are essential nutrients for bone health. Most people can get the recommended amounts of calcium through their diet, but supplementation may be needed for certain medical conditions. Recommendations suggest that vitamin D supplementation should be given to certain groups of people.
Calcium and vitamin D can be taken together, and several supplements offer a combined pill with both nutrients. Over-supplementing calcium and vitamin D can have significant and potentially dangerous side effects due to high calcium levels in the blood. Talk with a healthcare provider before starting any dietary supplements.
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