Does Forteo Cause High Calcium Levels?
Yes, Forteo (teriparatide) can cause high calcium levels in the blood, known as hypercalcemia. This occurs in up to 1.7% of patients in clinical studies, typically mild and transient, resolving without stopping treatment.[1][2]
How Does Forteo Lead to Hypercalcemia?
Forteo is a synthetic parathyroid hormone analog that stimulates bone formation but also increases calcium release from bones and absorption in the intestines/kidneys. This raises serum calcium, especially early in treatment or with higher doses. Monitoring is recommended, with levels checked periodically.[1][3]
How Common and Severe Is It?
Hypercalcemia affects 1-2% of users, more often in those with risk factors like dehydration or kidney issues. It's usually asymptomatic and mild (calcium 10.5-11.5 mg/dL), but severe cases (>12 mg/dL) may need dose adjustment or temporary pause.[1][2]
What Should Patients Watch For?
Symptoms include fatigue, nausea, constipation, confusion, or muscle weakness. If calcium exceeds 11 mg/dL or symptoms appear, contact a doctor—treatment often involves hydration or withholding doses until normalized.[1][3]
Who Is at Higher Risk?
Patients with hyperparathyroidism history, vitamin D excess, or concurrent thiazide diuretics face elevated risk. Forteo labeling advises caution in these groups and baseline calcium checks before starting.[1][2]
Management and Prevention Steps
- Measure serum calcium before and 1-2 months after starting, then periodically.
- Stay hydrated; avoid calcium supplements unless directed.
- If hypercalcemia develops, pause Forteo until resolved, then restart at reduced frequency if needed.[1][3]
Related Blood Changes Patients Ask About
Forteo may also transiently raise uric acid (up to 3%) or urinary calcium excretion, increasing kidney stone risk in predisposed individuals. Phosphate levels can drop.[1][2]
Sources
[1]: Forteo Prescribing Information (FDA)
[2]: Forteo Side Effects (Drugs.com)
[3]: Teriparatide Clinical Overview (Medscape)