Vitamin D helps the body absorb calcium and supports bone strength, muscle function, and normal immune activity. Toxicity is uncommon and usually follows prolonged, very high supplement doses—not ordinary sunlight exposure or food. Excess vitamin D can cause hypercalcemia, or elevated blood calcium. Warning signs may include persistent thirst, frequent urination, nausea, constipation, weakness, and confusion. Severe cases can involve kidney damage or abnormal heart rhythms, although these symptoms have many possible causes.
For most adults, recommended intake is 600 IU daily, rising to 800 IU after age 70. The usual adult upper intake level is 4,000 IU daily; higher treatment doses require medical supervision. Check multivitamins and calcium products for overlapping vitamin D. If you take high doses and develop concerning symptoms, contact a healthcare professional rather than assuming the cause or changing prescribed treatment yourself. Testing can clarify what is happening. The goal is enough vitamin D—not the highest possible dose.
