Vitamin D : Dosing, Safety and Interactions

by MedlinePlus

(Page 3 of 3)

Dosing

Standardization:

1 mg of cholecalciferol (vitamin D3) provides 40,000 IU vitamin D activity.

Sources of vitamin D:Vitamin D is obtained naturally from two sources: sunlight (ultraviolet light) and dietary consumption. Dietary sources of vitamin D include fatty fish (salmon, mackerel, tuna, sardines, and herring), vitamin D-fortified milk and cereal, eggs, and cod liver oil.

Adults (18 years and older):

U.S. Adequate Intake (AI) for adults:AI levels have been established by the U.S. Institute of Medicine of the National Academy of Sciences. Recommendations are: 5 mcg (200 IU) daily for all individuals (males, female, pregnant/lactating women) under the age of 50 years-old. For all individuals from 50-70 years-old, 10 mcg daily (400 IU) is recommended. For those who are over 70-years-old, 15 micrograms daily (600 IU) is suggested. Some authors have questioned whether the current recommended adequate levels are sufficient to meet physiological needs, particularly for individuals deprived of regular sun exposure. The upper limit (UL) for vitamin D has been recommended as 2,000 IU daily due to toxicities that can occur when taken in higher doses.

Multivitamins: Vitamin D is included in most multivitamins, usually in strengths from 50 IU to 1,000 IU as softgel, capsules, tablets, and liquid.

Rickets: Rickets may be treated gradually over several months or in a single day's dose. Gradual dosing may be 125-250 mcg (5000-10,000 IU) taken daily for 2-3 months, until recovery is well established and alkaline phosphatase blood concentration is close to normal limits. Single-day dosing may be 15,000 mcg (600,000 IU) of vitamin D, taken by mouth divided into 4-6 doses. Intramuscular injection is also an alternative for single-day dosing. For resistant rickets, some authors suggest a higher dose of 12,000 to 500,000 IU per day.

Hypoparathroidism:Dihydrotachysterol has been used in an oral initial dose of 750 mcg (0.75mg) to 2.5mg per day for several days. Maintenance: 200 mcg (0.2mg) to 1mg per day. Ergocalciferol has been used in an oral dose of 50,000 to 200,000 IU units daily concomitantly with calcium lactate 4 grams, six times per day.

Osteoporosis prevention:Ergocalciferol has been used in an oral dose of 400 to 800 IU per day.

Osteoporosis treatment: Ergocalciferol has been used in an oral dose of 400 to 800 IU per day (sometimes higher doses are used in conjunction with calcium).

Fracture prevention:Ergocalciferol has been used in an oral dose of 100,000 IU.

Hypocalcemia in chronic dialysis:Calcitriol has been used in an initial oral dose of 0.25 mcg per day. May increase by 0.25 mcg per day at 4 to 8 week intervals.

Renal osteodystophy:Calcitriol has been used in an oral dose of 0.25 mcg every other day to 3 mcg or more per day.

Psoriasis:Tacalcitol has been used topically as a 2 mcg/gram ointment applied twice daily.

Preventing multiple sclerosis:long-term consumption of at least 400 IU per day has been suggested.

Senile warts:Topical vitamin D(3) ointment has been applied to senile warts once or twice a day.

Children (younger than 18 years):

U.S. Adequate Intake (AI) and Tolerable Upper Intake levels (UL) for children: AI levels have been established by the U.S. Institute of Medicine of the National Academy of Sciences. Recommendations from birth until 50-year-old is 5mcg/day (200 IU/day). Children older than one year should not exceed the "upper limit" (UL) of 50 mcg (2000 IU) per day; children younger than one year should not exceed the UL of 25 mcg (1000 IU) per day. Vitamin D is possibly unsafe when used orally in excessive amounts, with adverse effects including hypercalcemia (high blood calcium levels). Some authors have questioned whether the current recommended adequate levels are sufficient to meet physiological needs, particularly for individuals deprived of regular sun exposure.

Rickets: Rickets may be treated gradually over several months or in a single day's dose. Gradual dosing may be 125-250 mcg (5000-10,000 IU) taken daily for 2-3 months, until recovery is well established and alkaline phosphatase blood concentration is close to normal limits. Single-day dosing may be 15,000 mcg (600,000 IU) of vitamin D, taken by mouth divided into 4-6 doses. Intramuscular injection is also an alternative for single-day dosing. For resistant rickets, some authors suggest a higher dose of 12,000 to 500,000 IU per day.

Hypoparathyroidism: Ergocalciferol has been used orally in an initial dose of 8,000 units/kg/day for 1-2 weeks. For maintenance, 2000 units/kg/day has been used.

Safety

Allergies:

Avoid or use caution with known hypersensitivity to vitamin D or any of its analogues and derivatives.

Side Effects and Warnings:

Vitamin D is generally well tolerated in recommended "Adequate Intake (AI)" doses.

Vitamin D Toxicity/Hypercalcemia (elevated blood calcium levels): Vitamin D toxicity can result from regular excess intake of this vitamin, and may lead to hypercalcemia and excess bone loss. In infants, vitamin D 1,000 mcg (40,000 IU) daily can cause toxicity in 1-4 months, and as little as 75 mcg (3,000 IU) daily may cause toxicity over years. In adults, toxic effects can occur with doses of 2,500 mcg (100,000 IU) taken daily for several months. Individuals at particular risk include those with hyperparathyroidism, kidney disease, sarcoidosis, tuberculosis, or histoplasmosis. 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/weight loss), followed by polyuria (excess urination), polydipsia (excess thirst), weakness, fatigue, somnolence, headache, anorexia, dry mouth, metallic taste, vertigo, 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. Blood levels of 25(OH)D3 levels may be significantly elevated, although 1,25(OH)2D3 levels may be normal. Treatment involves stopping 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.

Pregnancy and Breastfeeding:

Pregnancy: The recommended adequate intake for pregnant women is the same as for non-pregnant adults: 5 mcg (200 IU) daily under the age of 50-years-old, and 10 mcg (400 IU) daily for those ages 50-70 years-old. For all individuals from 50 to 70 years-old, 10 mcg daily (400 IU) is recommended. 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. Due to risks of vitamin D toxicity, any consideration of higher daily doses of vitamin D should be discussed with physician.

Lactation: Vitamin D is deficient in maternal milk, and to prevent deficiency and rickets in exclusively breast-fed infants, supplementation may be necessary, starting within the first two months of life. Human milk typically contains a vitamin D concentration of 25 IU/Liter or less. The recommended adequate intake of vitamin D to prevent vitamin D deficiency in normal infants, children, and adolescents is 200 IU per day.

Interactions

Interactions with Drugs:

Antacids (magnesium-containing): Hypermagnesemia (high blood magnesium levels) may develop when these agents are used concurrently with vitamin D, particularly in patients with chronic renal failure.

Anticonvulsants (Carbamazepine, Fosphenytoin, Phenytoin, Phenobarbital): Decreased vitamin D effects may occur with the use of certain anti-seizure drugs, as they may induce hepatic microsomal enzymes and accelerate the conversion of vitamin D to inactive metabolites.

Cholestyramine (Questran), Colestipol (Colestid): Intestinal absorption of vitamin D may be impaired with the use of these agents. Patients on cholestyramine or colestipol should be advised to allow as much time as possible between the ingestion of these drugs and vitamin D.

Corticosteroids: Use of corticosteroids can cause osteoporosis and calcium depletion with long-term administration. This calcium depletion creates a greater need for both supplemental calcium and vitamin D (which is necessary for calcium absorption).

Digoxin/Digitalis (cardiac glycosides): Vitamin D should be used with caution in patients taking digoxin, because hypercalcemia (which may result with excess vitamin D use) may precipitate abnormal heart rhythms.

Mineral oil: Intestinal absorption of vitamin D may be impaired with the use of mineral oil.

Orlistat (Xenical):Orlistat can reduce vitamin D levels. Patients should consider taking a multivitamin with fat-soluble vitamins at least 2 hours before or after orlistat, or at bedtime.

Rifampin (Rimactane): Rifampin increases vitamin D metabolism and reduces vitamin D blood levels. The need for vitamin D supplementation with rifampin has not been thoroughly studied, although additional supplementation may be necessary.

Stimulant laxatives (Bisacodyl, Cascara, Senna):Stimulant laxatives can reduce dietary vitamin D absorption. Stimulant laxatives should be limited to short-term use if possible.

Thiazide diuretics: Concurrent administration of thiazide diuretics and vitamin D to hypoparathyroid patients may cause hypercalcemia, which may be transient or may require discontinuation of vitamin D. Examples of thiazide diuretics include chlorothiazide (Diuril), chlorthalidone (Hygroton, Thalitone), hydrochlorothiazide (HCTZ, Esidrix, HydroDIURIL, Ortec, Microzide), indapamide (Lozol), and metolazone (Zaroxolyn).

Interactions with Herbs and Dietary Supplements:

Cardiac glycoside herbs:Vitamin D should be used with caution in patients taking herbs with similar properties on the heart as digoxin, because hypercalcemia (which may result with excess vitamin D use) may precipitate abnormal heart rhythms. Examples of cardiac glycoside herbs include: adonis ( Adonis vernalis ); Adonis microcarpa ; balloon cotton ( Asclepias friticosa ); black hellebore root/melampode ( Helleborus niger ); black Indian hemp ( Apocynum cannabinum ); bushman's poison ( Carissa acokanthera ); cactus grandifloris ( Selenicerus grandiflorus ); convallaria ( Convallaria majalis ); eyebright ( Euphrasia spp.); figwort ( Scrophulariaceae ); foxglove/digitalis ( Digitalis purpurea ); frangipani ( Plumeria rubra ); hedge mustard ( Sisymbruim officinale ); Helleborus viridus ; hemp root/Canadian hemp root; king's crown ( Calotropis procera ); lily-of-the-valley; motherwort ( Leonurus cardiaca ); oleander leaf ( Nerium oleander L.); pheasant's eye plant ( Adonis aestivalis ); plantain leaf ( Plantago lanceolata ); pleurisy root; psyllium husks ( Plantago psyllium ); redheaded cotton-bush ( Asclepias currassavica ); rhubarb root ( Rheum palmatum ); rubber vine ( Cryptostegia grandifolia ); sea-mango ( Cerebra manghas ); senna fruit ( Cassia senna ); squill ( Urginea maritima ); strophanthus ( Strophanthus hispidus , Strophanthus kombe ); uzara ( Xysmalobium undulatum ); wallflower ( Cheirantus cheiri ); white horehound ( Marrubium vulgare ); wintersweet ( Carissa spectabilis ); yellow dock root ( Rumex crispus ); and yellow oleander ( Thevetia peruviana ).

Calcium: Vitamin D is necessary for calcium absorption. Vitamin D is often included in calcium supplement products.

Interactions with Laboratory Tests:

Calcium blood levels: Hypercalcemia (elevated blood calcium levels) may occur with vitamin D toxicity.

Urinary calcium, phosphate: May increase with vitamin D intake.

Alkaline phosphatase blood levels: May decrease with vitamin D deficiency.

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