Understanding the Side Effects of Taking 1200 mg of Calcium a Day

November 13, 2025 •

4 min read

While 1200 mg of calcium daily is the recommended intake for women over 51, the body's total intake comes from food and supplements, not supplements alone. Understanding the potential side effects of taking 1200 mg of calcium a day, especially when derived primarily from supplements, is critical for safe and effective use.

Quick Summary

Taking 1200 mg of calcium, particularly from supplements, can cause gastrointestinal issues and increase the risk of kidney stones. Excessive intake may also lead to hypercalcemia, potentially affecting heart and kidney function over time.

Key Points

Gastrointestinal Distress: Calcium supplements, especially calcium carbonate, can cause constipation, gas, and bloating.
Increased Kidney Stone Risk: Excessive supplemental calcium intake is linked to a higher risk of developing kidney stones.
Hypercalcemia: Too much calcium can lead to hypercalcemia, an excess of calcium in the blood that can cause fatigue, confusion, and other systemic issues.
Potential Cardiovascular Concerns: Some research suggests a link between high-dose calcium supplements and an increased risk of cardiovascular events, although evidence is mixed.
Nutrient and Drug Interactions: High calcium intake can interfere with the absorption of other nutrients like iron and medications like thyroid hormones and certain antibiotics.
Vitamin D is Key: Your body needs sufficient vitamin D to effectively absorb the calcium you consume.

Recommended Intake Versus Total Intake

Many individuals focus solely on the dosage of their calcium supplement without considering their total daily intake from all sources. The Recommended Dietary Allowance (RDA) for adults, particularly women over 51 and adults over 70, is 1200 mg, but this includes calcium from all food and beverage sources. For adults aged 19–50, the RDA is 1000 mg. Because many dairy products, fortified foods, and vegetables contain calcium, adding a 1200 mg supplement to a calcium-rich diet can push the total intake well beyond the Tolerable Upper Intake Level (UL) and increase the risk of adverse effects.

Gastrointestinal Discomfort

The most commonly reported side effects of calcium supplementation are digestive in nature. These can include constipation, gas, and bloating. The specific form of calcium matters significantly. Calcium carbonate, which is often found in less expensive supplements and antacids like Tums, is notorious for causing constipation and is best absorbed with food. Calcium citrate, on the other hand, is absorbed well on an empty stomach and is less likely to cause these issues. Spreading out the dose throughout the day or switching supplement types can often alleviate these problems.

Potential for Kidney Stone Formation

For individuals with a history of kidney stones or those at high risk, excessive calcium supplementation is a major concern. Calcium oxalate stones are the most common type of kidney stone and can form when there are high levels of calcium and oxalate in the urine. Paradoxically, getting sufficient calcium from food can help prevent these stones by binding with oxalate in the gut and preventing its absorption. However, calcium from supplements may not offer the same protection and is linked to an increased risk of kidney stones. Maintaining proper hydration is also critical for diluting urine and preventing crystal formation.

The Risk of Hypercalcemia and Cardiovascular Issues

Hypercalcemia, or an abnormally high level of calcium in the blood, can result from excessive calcium intake, especially via supplements. While a well-functioning body normally regulates blood calcium tightly, very high intakes can overwhelm this process. Symptoms of hypercalcemia include increased thirst and urination, fatigue, nausea, and in severe cases, confusion and irregular heart rhythms.

There is also ongoing debate and mixed evidence regarding a link between high-dose calcium supplements and cardiovascular disease. Some studies suggest an increased risk of heart attack and stroke, especially in older adults, while others, particularly those including vitamin D, do not show this association. Some researchers theorize that supplemental calcium can cause unwanted calcification in arteries, though calcium from dietary sources does not appear to have the same effect.

Nutrient Interactions and Absorption

Calcium can interfere with the absorption of other important nutrients and medications. For instance, calcium can inhibit the absorption of iron, zinc, and magnesium. Taking calcium supplements alongside certain prescription medications, such as synthetic thyroid hormones (levothyroxine) and certain antibiotics (quinolones), can also reduce their effectiveness. Spacing out the intake of supplements and medications is crucial to avoid these interactions. Additionally, sufficient vitamin D is essential for the body to properly absorb calcium. If vitamin D levels are low, even high calcium intake will be inefficiently utilized by the body.

When to Reconsider Your Dosage

It is important to evaluate your need for a high-dose supplement. Many people can meet their daily calcium requirements through a balanced diet alone. Consulting with a healthcare provider can help determine your true needs based on your diet and medical history. For those who do need supplements, lower, more frequent doses (500 mg or less at a time) are absorbed more efficiently and may reduce the risk of side effects.

Comparison of Calcium Supplement Forms


Feature	Calcium Carbonate	Calcium Citrate
Elemental Calcium	Higher percentage (approx. 40%)	Lower percentage (approx. 21%)
Absorption with Food	Best absorbed when taken with meals	Absorbed well with or without food
Stomach Acid Requirement	Requires stomach acid for absorption	Doesn't require stomach acid for absorption (better for older adults or those on antacids)
Side Effects	More likely to cause constipation, gas, and bloating	Less likely to cause digestive issues
Cost	Generally less expensive	More expensive

Conclusion

While 1200 mg of calcium daily is a common recommendation, understanding the side effects is essential, especially when relying on supplements. Potential issues range from common digestive complaints to more serious concerns like kidney stones and hypercalcemia. Total daily intake, including from dietary sources, should always be considered. Consulting a healthcare professional to assess individual needs and risks is the most responsible approach to maintaining bone health and avoiding adverse effects from over-supplementation. For most, obtaining calcium from food is the safest option, with supplements used to fill specific gaps under medical guidance.

For further information on recommended calcium intake and sources, consult the NIH Office of Dietary Supplements website.

Frequently Asked Questions

For many adults, 1200 mg is the recommended daily intake, particularly for women over 51. However, this includes calcium from all food sources, not just supplements. Taking 1200 mg via a supplement on top of a calcium-rich diet can lead to excessive intake and potential side effects.

Initial symptoms of excessive calcium intake often include gastrointestinal issues like constipation, gas, or bloating. More advanced signs of hypercalcemia can include increased thirst, frequent urination, fatigue, and headaches.

To reduce side effects, try switching from calcium carbonate to calcium citrate, which is less likely to cause digestive upset. You can also split your dose into smaller amounts throughout the day, as the body absorbs calcium best in doses of 500 mg or less at a time.

High intake of calcium from supplements, particularly without proper hydration, can increase the risk of kidney stones. Ensuring adequate dietary calcium from food sources is generally seen as safer and may even help prevent kidney stones.

Some studies have suggested a link between high-dose calcium supplements and an increased risk of heart disease and arterial calcification, especially in older adults. However, the evidence is mixed, and experts recommend getting calcium primarily from diet.

Vitamin D is crucial because it helps your body absorb calcium from your diet and supplements. Without sufficient vitamin D, your body cannot use the calcium effectively, even if you are getting enough.

For optimal absorption and to minimize side effects, your body can absorb approximately 500 mg of calcium at a time. If you need a total of 1200 mg, it is better to take two or three smaller doses throughout the day.