What is Vitamin D-2: Uses, Warnings & Interactions

Medically reviewed by Karen Berger, Pharm.D.
Licensed Pharmacist
Updated May 14, 2025  •  Published Dec 30, 2020
Fact Checked

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Vitamin D-2 overview

BRAND NAMES:

  • Drisdol (Rx)

Generic Names:

  • Vitamin D2

  • Ergocalciferol

  • And others

Uses:

  • Increases the amount of vitamin D in your body. It also treats problems caused by not having enough calcium in the body, such as rickets. Ergocalciferol is a plant-based form of vitamin D.

Therapeutic Classes:

  • Vitamins

  • Calcium regulators

Forms:

  • Capsule

  • Tablet

  • Solution (liquid)

How it’s taken:

  • By mouth

What is Vitamin D-2 used for?

Vitamin D2 is used to prevent and treat low vitamin D levels in the body. It helps increase the amount of calcium that the body absorbs. Together, calcium and vitamin D supplements help with bone health, and support the immune system and brain health. 

Higher doses of vitamin D2, in prescription strength, can be used to treat:

  • Hypoparathyroidism (low levels of parathyroid hormone)

  • Refractory rickets (vitamin D-resistant rickets)

  • Familial hypophosphatemia (a rare condition associated with low vitamin D and phosphate levels in the blood 

Key takeaways

  • Vitamin D2 is a form of vitamin D. It is used to prevent and treat low vitamin D levels. It can also be used for other medical conditions. 

  • Take the exact dose your doctor recommends or prescribes. Do not take more medication than your doctor tells you to. Too much vitamin D can cause toxicity, which could be serious or life-threatening.

  • Signs of high vitamin D/calcium levels may include nausea, constipation, vomiting, appetite loss, increased thirst and urination, changes in mood, and feeling unusually tired. 

What form(s) does Vitamin D-2 come in

  • Prescription

    • Capsule: 50,000 units

    • Oral solution: 8,000 units per mL

  • OTC

    • Tablet: 400 IU (10mcg), 2000 IU (50mcg), and others

What are common Vitamin D-2 doses?

  • For vitamin D deficiency, a common OTC dose is 1,500 to 2,000 IU once daily. There are many different OTC products available, with varying strengths. Follow the instructions on the bottle, and consult your healthcare provider or pharmacist for medical advice if you have questions.

  • For vitamin D deficiency, a common prescription dose is 50,000 IU once weekly.

  • For vitamin D-resistant rickets: 12,000 to 500,000 IU daily

  • For hypoparathyroidism: 50,000 to 200,000 IU daily with calcium lactate

The dosage will be individualized for each patient. Because there is a small window between therapeutic and toxic doses, individuals who take higher doses of vitamin D2 will be closely monitored.

How to take Vitamin D-2

  • Your doctor will tell you how much medicine to use. Do not use more than directed.

  • Follow the instructions on the medicine label if you are using this medicine without a prescription.

  • Oral route: You may take this medicine with or without food.

  • Use the dropper that comes with the oral liquid to measure your dose. This medicine may either be mixed with foods such as cereal and fruit juice or dropped into the mouth.

What to do if you miss a dose of Vitamin D-2

  • Take a dose as soon as you remember. 

  • If it is almost time for your next dose, wait until then and take a regular dose. 

  • Do not take extra vitamin D2 to make up for a missed dose.

Vitamin D-2 contraindications

You should not take vitamin D2 if you:

  • Are allergic to vitamin D

  • Have hypercalcemia (high calcium levels in the blood)

  • Have malabsorption syndrome (a digestive system condition that prevents absorption of nutrients)

  • Are abnormally sensitive to the toxic effects of vitamin D

  • Have hypervitaminosis D (vitamin D toxicity)

Vitamin D-2 warnings

  • Make sure your doctor knows if you are pregnant or breastfeeding.

  • Make sure your healthcare provider knows about all health problems that you have.

Vitamin D-2 interactions

  • Tell your healthcare professional about all the medications you take, including prescription and over-the-counter drugs, vitamins, and dietary supplements.

  • Avoid antacids that contain aluminum (such as Maalox® or Mylanta®) while using this medicine.

Make sure your doctor knows if you are also using Questran (cholestyramine), mineral oil, Xenical (orlistat), or a diuretic (water pill) such as hydrochlorothiazide.

Vitamin D-2 side effects

Serious Side Effects

In rare cases, an allergic reaction may occur. If you have symptoms of hives, chest tightness, trouble breathing, or swelling of the face, lips, tongue, or throat, get emergency medical attention. 

Other serious side effects may occur. Report serious side effects to your doctor right away or get emergency medical help if your symptoms feel life-threatening or if you think you are having a medical emergency. Serious side effects may include:

  • Hypervitaminosis D (vitamin D toxicity): be alert to symptoms such as nausea, vomiting, constipation, appetite loss, increased thirst and urination, mood changes, extreme fatigue

  • Hypercalcemia (high calcium levels in the blood)

  • Hypercalciuria (excess calcium in the urine)

  • Hyperphosphatemia (high phosphate levels in the blood)

  • Kidney problems

  • Soft tissue calcification (buildup of calcium in body tissue)

  • Vascular calcification (buildup of calcium in the blood vessels)

  • Irregular heartbeat

  • Confusion

Common Side Effects

  • Diarrhea or constipation

  • Nausea and vomiting

  • Appetite loss

  • Dry mouth 

  • Headache 

  • Tiredness 

  • Metallic taste in the mouth

  • Pain in the bones and/or muscles

Sources:

Vitamin D-2 News & Research

The best time to take calcium with vitamin D3

Could vitamin D improve patient blood pressure?

Vitamin D side effects and how to avoid them

Vitamin D vs. D3: Differences, similarities, and which is better for you

When would I need a prescription for vitamin D?

How much vitamin D should I take?

Medically reviewed by Karen Berger, Pharm.D.
Licensed Pharmacist

After receiving her doctorate from the University of Pittsburgh School of Pharmacy, Karen Berger, Pharm.D., has worked in both chain and independent community pharmacies. She currently works at an independent pharmacy in New Jersey. Dr. Berger enjoys helping patients understand medical conditions and medications—both in person as a pharmacist, and online as a medical writer and reviewer.

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