Does celiac disease cause hypercalcemia?

December 10, 2025 •

4 min read

Untreated celiac disease most commonly results in low calcium levels due to intestinal malabsorption of vitamin D and calcium. However, high calcium levels, or hypercalcemia, can sometimes be observed in celiac patients through a complex interaction with other conditions.

Quick Summary

Celiac disease typically causes hypocalcemia and secondary hyperparathyroidism. Hypercalcemia is rare, often resulting from unmasked primary or tertiary hyperparathyroidism after starting a gluten-free diet, or due to excessive vitamin D supplementation.

Key Points

Hypocalcemia is the norm: Untreated celiac disease typically causes low blood calcium (hypocalcemia) due to the malabsorption of calcium and vitamin D.
Secondary Hyperparathyroidism: Chronic low calcium levels in untreated celiac disease can lead to secondary hyperparathyroidism, which increases bone resorption.
A GFD can unmask issues: Following a strict gluten-free diet can heal the intestine and normalize calcium absorption, which may reveal an underlying primary or tertiary hyperparathyroidism.
Hypercalcemia causes: Hypercalcemia in celiac patients is typically due to a pre-existing or developing issue like primary hyperparathyroidism, not the celiac disease itself.
Monitor calcium levels: Close monitoring of calcium and PTH levels is crucial, especially when starting a gluten-free diet, to detect potential underlying issues.
Bone health is a priority: Celiac disease significantly impacts bone health, with many patients showing low bone density at diagnosis, emphasizing the importance of correcting mineral deficiencies.

The Typical Effect of Celiac Disease: Low Calcium

For most individuals with undiagnosed or untreated celiac disease, the effect on calcium levels is the opposite of hypercalcemia. The immune-mediated damage to the small intestinal lining, particularly the duodenum where most calcium is absorbed, severely hinders the body's ability to absorb nutrients. This malabsorption of calcium and the fat-soluble vitamin D, which is essential for calcium absorption, leads to low levels of calcium in the blood (hypocalcemia).

In response to persistently low blood calcium, the parathyroid glands secrete more parathyroid hormone (PTH). This leads to a condition called secondary hyperparathyroidism (SHPT), where the body attempts to compensate by leaching calcium from the bones to raise blood levels. Over time, this chronic process can significantly weaken bones, causing osteopenia and osteoporosis.

The Paradox: Why Hypercalcemia Can Occur

While hypocalcemia is the norm for untreated celiac disease, hypercalcemia can manifest in a few specific, and often complex, scenarios. It is not a direct consequence of the celiac disease itself but rather results from other co-existing or secondary conditions. The healing of the intestinal lining following a gluten-free diet (GFD) is a critical factor in how these underlying issues are revealed.

Unmasking of Primary Hyperparathyroidism

Primary hyperparathyroidism (PHPT) is a condition typically caused by a benign tumor (adenoma) on a parathyroid gland, causing it to produce excess PTH independently of the body's calcium levels. In a patient with undiagnosed celiac disease, the malabsorption is so severe that it can prevent the body from absorbing enough calcium to even show high blood calcium levels from the PHPT. This is known as a "masked" presentation. Once the individual begins a strict GFD, the intestine heals, and calcium absorption improves dramatically. The excess PTH from the adenoma can now act on this newly absorbed calcium, causing a sudden and significant rise in blood calcium levels, thus unmasking the previously hidden PHPT.

Development of Tertiary Hyperparathyroidism

In long-standing, untreated celiac disease, the parathyroid glands are chronically overstimulated to produce PTH due to the persistent hypocalcemia. Over many years, the glands can become autonomous, meaning they continue to produce excess PTH even after the malabsorption is corrected and calcium levels would otherwise normalize. This is called tertiary hyperparathyroidism (THPT). After starting a GFD, the autonomous glands continue their overproduction, leading to hypercalcemia.

Excessive Supplementation

Following a celiac diagnosis, many patients are advised to take calcium and vitamin D supplements to correct long-standing deficiencies caused by malabsorption. When intestinal healing occurs on a GFD, the body's ability to absorb these supplements and dietary nutrients returns to normal. If supplementation dosages are not adjusted or are overly aggressive, this can lead to vitamin D intoxication and milk-alkali syndrome, both of which can cause severe hypercalcemia. For this reason, dosage and monitoring are crucial.

Comparison Table: Calcium Regulation in Celiac Disease


Condition	Typical Presentation	Underlying Cause	Role of Gluten-Free Diet (GFD)
Hypocalcemia	Low serum calcium levels, bone pain, cramps.	Intestinal malabsorption of calcium and vitamin D due to intestinal damage.	Corrects malabsorption and improves calcium absorption, reversing hypocalcemia.
Secondary Hyperparathyroidism (SHPT)	High PTH levels, low-to-normal calcium, bone resorption, osteoporosis.	Chronic hypocalcemia triggers compensatory PTH release from parathyroid glands.	Heals the intestine, normalizes calcium absorption, and resolves SHPT.
Unmasked Primary Hyperparathyroidism (PHPT)	Hypercalcemia observed after starting GFD, persistently high PTH.	Pre-existing autonomous parathyroid gland (adenoma) masked by celiac-induced malabsorption.	Improved absorption reveals the hypercalcemia, prompting investigation for PHPT.
Tertiary Hyperparathyroidism (THPT)	Hypercalcemia with autonomous, persistently high PTH after long-term SHPT.	Chronic stimulation of parathyroid glands leads to autonomous function.	Unmasks the autonomous gland activity, making the hypercalcemia apparent.

The Crucial Role of Diagnosis and Monitoring

The key to navigating these complex calcium issues is proper medical management. At the time of diagnosis, especially in adults with a long history of undiagnosed celiac disease, bone mineral density should be assessed. Blood tests for calcium, PTH, and vitamin D are also essential.

Lists of Calcium-Related Symptoms

Symptoms of Hypocalcemia (Low Calcium):

Muscle cramps and spasms
Numbness or tingling in fingers and toes
Convulsions
Severe bone pain or weakness
Fatigue

Symptoms of Hypercalcemia (High Calcium):

Fatigue and lethargy
Increased thirst and frequent urination
Abdominal pain and constipation
Bone pain
Kidney stones
Depression or memory loss

After beginning a GFD, re-evaluation of calcium, vitamin D, and PTH levels is critical. Improved intestinal absorption can dramatically change the metabolic picture. For instance, a patient with SHPT at diagnosis may see their PTH levels normalize on a GFD. Conversely, a patient with previously normal or low-normal calcium levels might develop hypercalcemia, signaling an underlying issue like PHPT. In such cases, further investigation is warranted, which may include imaging of the parathyroid glands. For more information on celiac disease management, visit the Celiac Disease Foundation.

Conclusion

In summary, celiac disease itself does not cause hypercalcemia; in fact, it typically leads to the opposite condition, hypocalcemia, due to intestinal malabsorption. However, the initiation of a gluten-free diet can have a profound effect on mineral balance. By healing the gut and restoring absorption, a GFD can reveal an underlying primary hyperparathyroidism or a long-standing tertiary hyperparathyroidism that was previously masked. Comprehensive monitoring of calcium, vitamin D, and PTH levels is therefore a critical component of managing celiac disease, especially during the first year of treatment, to ensure any potential calcium-related issues are properly addressed.

Frequently Asked Questions

A gluten-free diet does not directly cause high calcium levels. However, by healing the intestinal damage and restoring normal absorption, it can unmask pre-existing or developing conditions like hyperparathyroidism, which then cause elevated calcium levels.

The most common calcium issue in untreated celiac disease is hypocalcemia, or low blood calcium. This is a direct result of the damaged intestine's inability to properly absorb calcium and vitamin D from food.

Secondary hyperparathyroidism is a condition where the parathyroid glands work overtime, producing excess PTH in an attempt to compensate for the chronically low blood calcium levels caused by intestinal malabsorption in celiac disease.

In primary hyperparathyroidism, an overactive parathyroid gland causes excess calcium to be released into the blood. In a patient with untreated celiac disease, the severe malabsorption can counteract this, keeping blood calcium levels from rising. The hypercalcemia only becomes apparent when a gluten-free diet is initiated and intestinal absorption improves.

A celiac patient would require a parathyroidectomy if they are diagnosed with primary hyperparathyroidism, typically caused by a parathyroid adenoma. This surgical removal of the affected gland addresses the root cause of the hypercalcemia.

Healthcare providers monitor calcium levels through blood tests, often alongside vitamin D and PTH levels. This is especially important during the first few months to a year of starting a gluten-free diet to ensure that mineral balance is normalizing and not revealing any underlying issues.

Yes, untreated celiac disease is a significant risk factor for osteoporosis. The long-term malabsorption of calcium and vitamin D leads to weakened bones and decreased bone mineral density, increasing the risk of fractures.