Can a Person Overdose on Calcium?

You probably won't overdose on calcium from natural foods.
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Calcium is essential for keeping your bones and teeth strong and helps to regulate muscle contractions, including the heart. However, calcium toxicity can result from supplement overdose. The consequences can be dangerous, leading to soft tissue calcification and life-threatening organ dysfunction.



Although there is little likelihood you could overdose on calcium from food, taking too many supplements could risk damage to your kidneys and heart.

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Why Do You Need Calcium?

Your body needs calcium to support many crucial metabolic functions. Calcium is vital to help signaling between cells, vascular contraction and secretion of certain hormones and enzymes.

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Your skeletal and dental health depends on calcium. Bones serve as the major reservoir and contain 99 percent of your body's calcium supply, according to National Institutes of Health (NIH). Bone tissue is used to maintain constant concentration of calcium in your blood, muscles and intercellular fluid.

For those who cannot get adequate calcium from their diet, supplemental calcium is often prescribed to help prevent bone loss and fractures, especially in patients with rheumatoid arthritis and other inflammatory diseases. The NIH points out that many women look to the benefits of calcium supplements to help boost bone density, especially after menopause, and to reduce the risk of osteoporosis.

How Much Do You Need?

The Food and Nutrition Board has established the amount of calcium you need for bone health and to maintain adequate retention. This recommended intake includes sources from food as well as supplements containing calcium. The daily dietary allowances, depending on age and gender are:


  • Children, ages 1 to 3: 500 milligrams; ages 4 to 8: 800 milligrams
  • Adults, ages 19 to 50 years: 1,000 milligrams
  • Adults, ages 51 to 70 years: Males, 800 milligrams; Females, 1,000 milligrams
  • Adults, ages 71 years and older: 1,000 milligrams
  • Pregnant and lactating women: 800 to 1,000 milligrams

The best natural sources of calcium come from dairy products, such as milk, yogurt and cheese. Leafy green vegetables contain calcium but spinach has poor bioavailability. Many foods are fortified, including fruit juices and drinks, cereals and products made from grain. Some good sources of calcium include:


  • Tofu, firm, prepared with calcium sulfate
  • Milk, including low-fat, 2 percent, whole milk, buttermilk
  • Yogurt, including fresh and frozen
  • Cheese, including Parmesan, ricotta, Gruyere
  • Leafy greens, including spinach, collard, turnip, kale
  • Legumes, including black-eyed peas, green soybeans, white beans
  • Canned fish, including sardines, pink salmon


Why Would You Need Supplementation?

Although it's best to meet your calcium needs from food, calcium supplements may be useful if your diet falls short or if your body has difficulty absorbing enough calcium to meet its requirements. When your reserves are low, your body takes calcium from your bones.


Some reasons you may be at risk for low calcium could result from certain conditions that may include:

  • Vegetarian or vegan diet
  • Lactose intolerance
  • Intestinal problems with absorbing calcium or certain medical conditions, such as celiac or inflammatory bowel disease
  • Osteoporosis
  • Long-term treatment with corticosteroids
  • Pregnancy

If you think you have a calcium deficiency that can't be rectified by your diet, you should consider taking advantage of the benefits of calcium supplements. Be sure to check with your health care professional, as different forms of supplements contain various amounts of elemental calcium, depending on the type of salt used.


Elemental calcium is the calcium that your body can actually absorb and metabolize. Calcium carbonate and calcium citrate are the most commonly used forms of calcium supplements available. Calcium supplements can be taken in various forms, such as oral and chewable tablets, capsules, liquids and powders.

Calcium supplements should be taken with food for best absorption, according to the NIH. Additionally, research suggests that large doses of supplemental calcium, taken separate from a meal, may lead to kidney stone formation, according to a study published in Translational Andrology and Urology in September 2014.


Read more: The Different Ways Calcium Citrate and Calcium Carbonate Help Bones

Calcium Overdose and Toxicity

It is extremely unlikely you could get a calcium overdose from food alone, but taking too many calcium supplements has the potential of toxicity. Calcium overdose from supplements can weaken your bones, lead to kidney stones, reduce nutrient absorption and interfere with the health of your heart, says the NIH.



Because of the risks associated with calcium toxicity, the Food and Nutrition Board has established Tolerable Upper Intake Levels for calcium. These recommendations are:

  • Infants: 0 to 6 months: 1,000 milligrams; 6 to 12 months: 1,500 milligrams
  • Children: ages 1 to 8 years: 2,500 milligrams; ages 9 to 18 years, 3,000 milligrams
  • Adults, ages 19 to 50 years: 2,500 milligrams
  • Adults, ages 51 years and older: 2,000 milligrams
  • Pregnant and lactating women: 2,500 to 3,000 milligrams

If you take calcium supplements for your bones, exceeding the recommended dose will not necessarily provide any extra benefit. Calcium supplements are best absorbed when taken in small doses of 500 milligrams or less at mealtimes.

Bone health is dependent on not only calcium but its interaction with vitamins D, K and magnesium for proper utilization and metabolism. Overuse of calcium supplements may do more harm than good and could result in dangerously high levels of calcium in your blood.

Tums Overdose Symptoms

Many dietary supplements and some antacids for heartburn, such as Tums, contain calcium carbonate that may cause calcium supplements side effects. If you take more than the recommended dose, calcium carbonate can be harmful. The Mayo Clinic reports that symptoms of calcium carbonate toxicity include:

  • Thirst
  • Bone pain
  • Confusion
  • Constipation or Diarrhea
  • Depression
  • Headache
  • Irregular heartbeat
  • Loss of appetite
  • Muscle twitching
  • Nausea, vomiting

It is unlikely you could die from an antacid overdose. Calcium carbonate is not extremely poisonous. Recovery is likely, but long-term overuse can be more serious than a single overdose because it can result in kidney damage.

Risk of Hypercalcemia

Taking excessive amounts of calcium from supplements in amounts from 1.5 to 16.5 grams per day long-term can raise calcium levels in your blood above normal, which could develop into hypercalcemia. If left untreated, hypercalcemia can affect your nervous system, heart, stomach, kidneys and bones.


Side effects of severe hypercalcemia from calcium overdose may include:

  • Nausea
  • Vomiting
  • Constipation
  • Abdominal pain
  • Frequent urination
  • High blood pressure
  • Bone pain, muscle weakness
  • Delirium, confusion, lethargy and fatigue

In rare cases, the Mayo Clinic reports that severe hypercalcemia can interfere with your heart function, causing heart arrhythmia, such as palpitations and fainting. Without treatment, hypercalcemia may lead to coma and even death.

Read more: The Safest Ways to Take Potassium, Magnesium and Calcium Supplements

Interaction With Medications

Calcium supplements have the potential to interact with several types of prescription drugs. Consult your doctor if you are on any medications before taking calcium supplements.

Calcium carbonate can react with thiazide diuretics, often referred to as water pills for high blood pressure. The interaction can cause a shift in the body's acid-to-base balance and increase the risk of hypercalcemia. Calcium can decrease effectiveness of drugs that treat osteoporosis, some antibiotics, anticonvulsants and medications used to treat Paget's disease.

Antacids that contain aluminum or magnesium may increase urinary calcium excretion. Certain laxatives and mineral oil can decrease calcium absorption. Long-term use of prednisone and similar drugs can also cause calcium depletion, leading to osteoporosis.




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