The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.
Avoid with known allergy/hypersensitivity to vitamin D, any of its analogs and derivatives, or any component of the formulation.
Side Effects and Warnings
Vitamin D is generally well tolerated in recommended "adequate intake (AI)" doses.
The Institute of Medicine (IOM) released a report on November 30, 2010, recommending vitamin D upper intake levels (UL) of 3,000 IU for those less than nine years old and 4,000 IU for those over nine years old. According to the Institute of Medicine, recommended upper intake levels (ULs) of vitamin D are 1,000 IU for ages 0-6 months, 1,500 IU for ages 7-12 months, 2,500 IU for ages 1-3 years, 3,000 IU for ages 4-8 years, and 4,000 IU for those over age nine. A clinical review has suggested the use of 250 micrograms (10,000 IU) of vitamin D3 daily as the UL, based on the lack of observed toxicity in adult trials.
Excess vitamin D intake may increase the risk of falls or fractures. Other potential adverse effects include increased risk of urinary tract infections, decreased appetite, weight loss, an elevated international normalized ratio, hypercalcemia (increased calcium in the blood), hypercalciuria (increased calcium in the urine), hypervitaminosis D (high blood levels of vitamin D), elevated creatinine levels, gastrointestinal complaints, and increased cancer risk.
Vitamin D toxicity can result from regular excess intake of this vitamin and may lead to hypercalcemia, hypercalciuria, and excess bone loss. Individuals at particular risk include those with hyperparathyroidism (overactive parathyroids), kidney disease, sarcoidosis, tuberculosis, or histoplasmosis (examples of immune disorders). Chronic hypercalcemia may lead to serious or even life-threatening complications and should be managed by a physician. Early symptoms of hypercalcemia may include nausea, vomiting, and anorexia (appetite or weight loss), followed by polyuria (excess urination), polydipsia (excess thirst), weakness, fatigue, somnolence, headache, dry mouth, a metallic taste, vertigo (dizziness), tinnitus (ear ringing), and ataxia (unsteadiness). Kidney function may become impaired, and metastatic calcifications (calcium deposition in organs throughout the body) may occur, particularly affecting the kidneys. Treatment involves stopping the intake of vitamin D or calcium and lowering the calcium levels under strict medical supervision, with frequent monitoring of calcium levels. Acidification of urine and corticosteroids may be necessary. To return vitamin D levels to normal, the supplement is discontinued.
One study found a greater likelihood of daytime sleepiness for patients given vitamin D analogs. Other adverse effects associated with topical vitamin D analogs include coronary and vascular calcification. Topical vitamin D analogs may be associated with contact dermatitis and skin irritation.
Vitamin D may lower blood sugar levels. Caution is advised in patients with diabetes or hypoglycemia and in those taking drugs, herbs, or supplements that affect blood sugar. Blood glucose levels may need to be monitored by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.
Vitamin D may cause low blood pressure. Caution is advised in patients taking herbs or supplements that lower blood pressure.
Use cautiously in patients with liver disease, as vitamin D is metabolized in the liver.
Use cautiously in patients with hyperparathyroidism, as vitamin D may increase calcium levels.
Use cautiously in patients with kidney disease, as vitamin D may increase calcium levels and increase the risk of arteriosclerosis.
Use cautiously in patients with granulomatous disorders (a type of immune disorder), which are associated with calcium metabolism disorder. Theoretically, concurrent use of high amounts of vitamin D in these patients may increase the risk of hypercalcemia (increased calcium in the blood) and kidney stones.
Use cautiously in mothers who are receiving vitamin D supplements and are breastfeeding, as there may be an increased risk of urinary tract infection, particularly in the first three months.
Avoid in individuals with known allergy to vitamin D or with vitamin D hypersensitivity syndromes.
Avoid in patients with hypercalcemia (high blood calcium levels), due to the potential for increased blood calcium levels.
Pregnancy and Breastfeeding
Many pregnant women around the world have been found to be vitamin D deficient. The recommended adequate intake for pregnant women is the same as for nonpregnant adults. Most prenatal vitamins provide 400 IU daily of vitamin D as cholecalciferol. Some authors have suggested that requirements during pregnancy may be greater than these amounts, particularly in sun-deprived individuals, although this has not been clearly established. Risk factors for developing vitamin D deficiency during pregnancy include darker pigmentation, sunscreen use, clothing, latitude, seasons, obesity, race, ethnicity, and low intake of fortified vitamin D milk intake. Due to risks of vitamin D toxicity, any consideration of higher daily doses of vitamin D should be discussed with a physician. Vitamin D deficiency may increase complications in the mother and infant.
In mothers who are receiving vitamin D supplements and are breastfeeding, there may be an increased risk of urinary tract infection, particularly in the first three months.
Vitamin D is typically low in maternal milk, and to prevent deficiency and rickets in exclusively breastfed infants, supplementation may be necessary, starting within the first two months of life. Many lactating women have been found to be vitamin D deficient.