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Side Effects and Warning for vitamin D

University of Maryland July 2010

Side effects may include:

  • Excessive thirst
  • Metal taste in the mouth
  • Poor appetite
  • Weight loss
  • Bone pain
  • Tiredness
  • Sore eyes
  • Itchy skin
  • Vomiting
  • Diarrhea
  • Constipation
  • A frequent need to urinate
  • Muscle problems

You cannot get too much vitamin D from sunlight, and it would be very hard to get too much from food.

Generally, too much vitamin D is a result of taking supplements in too high a dose.

People with the following conditions should be careful when considering taking vitamin D supplements:

  • High blood calcium or phosphorus levels
  • Heart problems
  • Kidney disease

Possible Interactions:

If you are currently being treated with any of the following medications, you should not use vitamin D supplements without first talking to your healthcare provider.

  • Atorvastatin (Lipitor) - Taking vitamin D may reduce the amount of Lipitor absorbed by the body, making it less effective. If you take Lipitor or any statin (drugs used to lower cholesterol), ask your doctor before taking vitamin D.
  • Calcium channel blockers - Vitamin D may interfere with these medications, used to treat high blood pressure and heart conditions. If you take any of these medications, do not take vitamin D without first asking your doctor. Calcium channel blockers include:
  • Nifedipine (Procardia)
  • Verapamil (Calan)
  • Nicardipine (Cardene)
  • Diltiasem (Cardizem, Dilacor)
  • Amlodipine (Norvasc)
  • Corticosteroids (prednisone) - Taking corticosteroids long-term can cause bone loss leading to osteoporosis. Supplements of calcium and vitamin D can help maintain bone strength. If you take corticosteroids for 6 months or more, ask your doctor about taking a calcium and vitamin D supplement.
  • Digoxin (Lanoxin) - a medication used to treat irregular heart rhythms. Vitamin D improves the absorption of calcium, and calcium, in turn, can increase the likelihood of a toxic reaction from this medication.

These drugs may raise the amount of vitamin D in the blood:

  • Estrogen - Hormone replacement therapy with estrogen appears to raise vitamin D levels in the blood, which may have a positive effect on calcium and bone strength. In addition, taking vitamin D supplements along with estrogen replacement therapy (ERT) increases bone mass more than ERT alone. However, this benefit may be lost with the addition of progesterone.
  • Isoniazid (INH) — a medication used to treat tuberculosis.
  • Thiazide — This kind of diuretic (water pills) can increase vitamin D activity and can lead to high calcium levels in the blood.

Vitamin D levels may be decreased by the following medications.

If you take any of these medications, ask your doctor if you need more vitamin D:

Antacids - Taking certain antacids for long periods of time may alter the levels, metabolism, and availability of vitamin D.

Anti-seizure medications - these medications include:

  • Phenobarbital
  • Phenytoin (Dilantin)
  • Primidone (Mysoline)
  • Valproic acid (Depakote)

Bile acid sequestrants - are used to lower cholesterol. These medications include

  • Cholestyramine (Questran, Prevalite)
  • Cholestipol (Colestid)
  • Rifampin - used to treat tuberculosis
  • Mineral oil - Mineral oil also interferes with the absorption of vitamin D.
  • Orlistat (Alli) - a medication used for weight loss that prevents the absorption of fat.
    • Because of its effect on fat, orlistat may also prevent the absorption of fat-soluble vitamins such as vitamin D. Physicians who prescribe orlistat also add a multivitamin with fat-soluble vitamins.

NLM July 2010

Side Effects and Warnings

  • Vitamin D is generally well tolerated in recommended "Adequate Intake (AI)" doses. One study found a greater likelihood of daytime sleepiness for patients given vitamin D analogs.
  • Vitamin D toxicity can result from regular excess intake of this vitamin and may lead to hypercalcemia and excess bone loss. 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, 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. 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.


Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. 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.

Interactions with Drugs

  • Hypermagnesemia (high blood magnesium levels) may develop when magnesium-containing antacids are used concurrently with vitamin D, particularly in patients with chronic renal failure.
  • 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.
  • Based on the mechanism of action, the use of vitamin D and calcium together may alter the inflammatory response.
  • 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.
  • The 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).
  • Vitamin D should be used with caution in patients taking digoxin because hypercalcemia (which may result from excess vitamin D use) may precipitate abnormal heart rhythms.
  • Intestinal absorption of vitamin D may be impaired with the use of mineral oil.
  • Orlistat (an obesity drug) can reduce vitamin D levels. Patients should consider taking a multivitamin with fat-soluble vitamins at least two hours before or after orlistat or at bedtime.
  • 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 can reduce dietary vitamin D absorption. Stimulant laxatives should be limited to short-term use if possible.
  • 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

  • Based on the mechanism of action, the use of vitamin D and calcium together may alter the inflammatory response.
  • Vitamin D should be used with caution in patients taking herbs with similar properties on the heart as digoxin because hypercalcemia (which may result from excess vitamin D use) may precipitate abnormal heart rhythms.
  • Vitamin D is necessary for calcium absorption. Vitamin D is often included in calcium supplement products.

See also VitaminDWiki

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