Minerals
Calcium
Calcium is an essential mineral. It provides structure to bones and teeth and contributes to normal muscle function, nerve transmission and blood clotting.
Calcium is a major mineral, meaning your body needs it in relatively larger amounts than trace minerals. You can obtain it from dairy products, calcium-fortified foods and certain green vegetables. Vitamin D supports its absorption in the intestine. In food and in the body, calcium occurs in compounds or as calcium ions, not as metallic calcium. Calcium carbonate and calcium citrate are compounds that supply calcium; they are distinct from the nutrient itself.
Calcium is an essential mineral that you obtain through your diet. It provides structure to bones and teeth and has other important roles in the body. Vitamin D supports calcium absorption in the intestine.
Why your body needs calcium
Calcium is needed for the maintenance of normal bones and teeth. It also contributes to normal muscle function, neurotransmission, blood clotting and energy-yielding metabolism. It has a role in cell division and specialisation too. These functions do not mean that extra calcium improves strength or concentration, or prevents fractures, when intake is already adequate.
Getting calcium from food
Sources include milk and dairy products, calcium-fortified foods and certain green vegetables such as kale and broccoli. Water can also contribute, depending on its calcium content. Content is not the only consideration: oxalate and phytate can reduce absorption in the gut. Calcium from oxalate-rich spinach is therefore less bioavailable than calcium from kale or broccoli.
A normal blood calcium level does not reliably show whether you get enough calcium. Your body regulates this level very tightly. Dietary intake therefore also needs to be considered when assessing calcium adequacy.
What to know about calcium supplements
Calcium carbonate and calcium citrate are compounds that supply calcium. Calcium carbonate absorption benefits from being taken with a meal; calcium citrate is less dependent on stomach acid and can be taken without food. Amounts refer to elemental calcium, not the total weight of the compound. Supplements can cause constipation, gas and bloating. Not everyone needs a calcium supplement.
Findings on calcium supplements and kidney stones or cardiovascular events are mixed. These uncertainties are not a reason to avoid calcium-containing foods across the board. Discuss your needs and the likely benefit before taking supplements long term.
How nutrition works
Bone health
Calcium is needed for the maintenance of normal bones. [1]
Dental health
Calcium is needed for the maintenance of normal teeth. [1]
Muscle function
Calcium contributes to normal muscle function. [1]
Nervous system
Calcium contributes to normal neurotransmission. [1]
Energy metabolism
Calcium contributes to normal energy-yielding metabolism. [1]
Cell division
Calcium has a role in the process of cell division and specialisation. [1]
Blood pressure
Blood coagulation
Calcium contributes to normal blood clotting. [1]
Body weight
In adults with overweight or obesity, calcium supplements may have little or no effect on body weight. [3]
Cardiovascular health
A general cardiovascular benefit from calcium supplements is unproven, and evidence of possible harm is inconsistent. [4]
Statements & evidence
EFSA sets a population reference intake for calcium of 1,000 mg daily for adults aged 18–24 and 950 mg daily from age 25. [5]
These values guide intake in healthy population groups; they are not measurements of an individual’s requirements. EFSA does not specify an increase during pregnancy or breastfeeding above the corresponding age-specific value.
The EU nutrient reference value for calcium used on adult food labels is 800 mg. [6][5]
Calcium percentages on labels are calculated using this labelling reference value. It is distinct from EFSA’s age-specific intake reference values.
EFSA has established a tolerable upper intake level of 2,500 mg calcium daily for adults, including during pregnancy and breastfeeding. [7]
This applies to habitual total intake from food and supplements combined. It is an upper safety reference, not a daily intake target.
Milk and dairy products are often important calcium sources in European diets. Hard water can also contribute to calcium intake. [8]
Their contribution depends on food choices and the calcium content of the water. This is qualitative source information, not a statement of calcium amounts in individual foods.
Calcium is not absorbed equally well from all foods. Oxalate and phytate can reduce its absorption in the gut. [4]
For example, calcium in oxalate-rich spinach is less bioavailable than calcium in low-oxalate vegetables such as kale and broccoli. Both calcium content and the proportion absorbed matter for dietary supply.
Calcium carbonate absorption depends more on stomach acid and benefits from being taken with a meal. Calcium citrate is less acid-dependent and can be taken without food. [4]
If you use a calcium supplement, check its calcium compound and follow the product’s instructions. These differences do not mean that everyone needs a calcium supplement.
The proportion of calcium absorbed decreases as a single dose increases. NIH ODS reports that absorption from supplements is highest at single doses of 500 mg or less. [4]
The amount refers to elemental calcium, not the total weight of the calcium compound. It is not a recommendation to take an additional 500 mg every day.
A normal blood calcium level does not reliably show whether dietary calcium intake is adequate. [4]
The body tightly regulates blood calcium. This measurement alone is therefore not a suitable indicator of dietary calcium adequacy; dietary intake also needs to be considered.
Safety information
Upper level · Adults
Upper limit for total daily intake
EFSA sets a tolerable upper intake level of 2,500 mg calcium per day for adults, including pregnant and breastfeeding adults. Count calcium from food, fortified products, supplements and calcium-containing medicines together. This means elemental calcium, not the weight of the calcium salt. The limit applies to habitual intake and is not an intake target; kidney disease or abnormal calcium metabolism requires individual advice. [7][4]
Upper level
No EFSA upper limit established for children
EFSA could not establish a tolerable upper intake level for infants, children or adolescents because the evidence was insufficient. This does not mean unlimited intake is safe. Do not apply adult supplement doses to children; use age-appropriate products with professional advice. [7]
Upper level
BfR recommendation for supplements
Germany’s BfR recommends a maximum of 500 mg calcium per recommended daily dose of a supplement. Products providing more than 250 mg per day should warn against taking another calcium-containing supplement. This recommendation is not a statutory maximum and is distinct from the upper limit for total intake. [9]
Side effect
Constipation and bloating from calcium supplements
Calcium supplements can cause constipation, gas and bloating. Calcium carbonate appears more likely to cause these effects than calcium citrate, particularly in older people with less stomach acid. Frequency and tolerability depend on the product and the individual. [4]
Side effect
Overdose can raise calcium levels
Excessive calcium intake, particularly from supplements or calcium-containing antacids, can raise calcium in the blood or urine. Severe or persistent hypercalcaemia can damage the kidneys and cause heart rhythm disturbances. Seek prompt medical assessment for marked thirst, frequent urination, vomiting, pronounced weakness or confusion after high intake. This warning does not concern ordinary calcium intake from food. [10][4]
Side effect
Calcium–alkali syndrome with excessive use
Excessive intake of calcium and absorbable alkali, for example from calcium carbonate supplements or antacids, can cause calcium–alkali syndrome. This combines high blood calcium, metabolic alkalosis and impaired kidney function. Avoid combining these products without checking the total intake. [11]
Contraindication
Existing conditions can rule out certain products
Calcium/vitamin D medicines may be contraindicated in people with existing high blood or urinary calcium, renal failure, kidney stones or calcium deposits in the kidneys. Excess vitamin D is an additional possible contraindication for combination products. Exact restrictions are product-specific: do not start treatment without medical review. These restrictions do not amount to a blanket ban on calcium-containing foods. [12]
Caution
Extra care with kidney impairment and sarcoidosis
People with impaired kidney function, sarcoidosis or osteoporosis with prolonged immobility should use calcium/vitamin D products only after medical advice. Calcium and kidney function monitoring may be needed. This is particularly relevant to older people who also have kidney problems or take several medicines. [12][10]
Interaction
Separate calcium from levothyroxine
Calcium supplements can reduce levothyroxine absorption. NIH reports a separation of at least four hours for calcium carbonate. If you take levothyroxine, follow your medicine’s instructions and check the dosing schedule with a pharmacist or clinician. [4]
Interaction
Interactions with certain antibiotics and bisphosphonates
Calcium can reduce the absorption of tetracyclines, fluoroquinolones and oral bisphosphonates. If you take one of these medicines, follow its specific instructions for separation from calcium products. There is no universal spacing rule for all medicines; instructions concerning food can also differ. [12]
Interaction
Dolutegravir timing depends on food
If you take dolutegravir, EMA permits calcium supplements to be taken at the same time when taken with food. When fasting, take dolutegravir at least two hours before or six hours after the calcium supplement. Follow the instructions from your HIV treatment team. [13]
Interaction
Thiazides and lithium can favour high calcium levels
Thiazide diuretics reduce urinary calcium excretion, while long-term lithium treatment can also cause high blood calcium. Calcium supplements may increase the risk further. If you take either medicine, check whether supplementation is suitable and whether calcium monitoring is needed. [12][4]
Interaction
Extra caution with digoxin and other cardiac glycosides
If you take digoxin or another cardiac glycoside, high blood calcium can increase toxicity and the risk of heart rhythm disturbances. Do not start calcium/vitamin D products without medical advice. Calcium measurements and ECG monitoring may be needed. [12]
Caution
Choose products carefully during pregnancy and breastfeeding
The EFSA adult upper limit applies during pregnancy and breastfeeding, but it does not establish the suitability of every calcium/vitamin D product. Avoid overdose and follow product-specific instructions and maternity-care advice. Persistent maternal hypercalcaemia can harm the unborn child. [7][12]
Caution
Kidney stone risk from supplements is uncertain
Evidence on kidney stones with calcium supplements is mixed: some data suggest increased risk, while other findings show no clear increase. If you have had kidney stones, seek an individual assessment before supplementing. This uncertainty about supplements is not a reason to avoid calcium-containing foods across the board. [4][7]
Caution · Adults
Cardiovascular risks from calcium supplements remain uncertain
Studies of calcium supplements and cardiovascular events in adults give conflicting results. A causal increase in heart attacks or strokes is not established, although small additional risks cannot be reliably excluded. This does not imply a warning against ordinary dietary calcium. Discuss the need and likely benefit before taking supplements long term. [4]
Frequently asked questions
How much calcium do I need each day?
EFSA sets a population reference intake of 1,000 mg calcium daily for healthy adults aged 18–24 and 950 mg from age 25. The same age-specific values apply during pregnancy and breastfeeding.
Which foods provide calcium?
Calcium sources include dairy products, calcium-fortified foods and certain green vegetables such as kale and broccoli. Calcium from oxalate-rich spinach is less well absorbed than calcium from these low-oxalate vegetables.
What is the difference between calcium carbonate and calcium citrate?
Calcium carbonate absorption depends more on stomach acid and benefits from being taken with a meal. Calcium citrate is less acid-dependent and can be taken without food; follow your product’s instructions.
Can I get too much calcium?
Yes: excessive intake, particularly from supplements or calcium-containing antacids, can raise calcium levels in the blood or urine. EFSA’s adult upper limit is 2,500 mg daily from all sources combined, including during pregnancy and breastfeeding; it is not an intake target.
Does a normal blood calcium level mean I get enough calcium?
Not reliably: your body tightly regulates blood calcium levels. Dietary intake also needs to be considered when assessing whether you get enough calcium.
More entries
Iodine
Iodine is an essential trace mineral. Your body needs it to make thyroid hormones, which help regulate metabolism and support growth and development.
Iron
Iron is an essential trace element and a component of haemoglobin, which transports oxygen in the blood.
Selenium
Selenium is an essential trace element. Your body needs small amounts to make selenium-containing proteins involved in thyroid hormone metabolism and protection against oxidative damage.
Zinc
Zinc is an essential trace element that you obtain through your diet. It has important roles in enzymes and other proteins.
Magnesium
Magnesium is an essential mineral. Your body needs it for energy metabolism, normal muscle and nerve function, and bone structure, among other roles.
Potassium
Potassium is an essential mineral and electrolyte. It supports normal nerve and muscle function and helps regulate the distribution of fluid in the body.
Sources
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