Vitamin D

Over-the-counter

What is Vitamin D?

Vitamin D is a fat-soluble vitamin that your body needs to absorb calcium and maintain healthy bones. Your skin makes vitamin D naturally when exposed to sunlight. However, many people do not get enough sun exposure or dietary vitamin D to meet their needs. This makes supplementation important for bone health, immune function, and overall wellness.

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Vitamin D comes in two main forms. Vitamin D2, also called ergocalciferol, comes from plant sources and fortified foods. Vitamin D3, also called cholecalciferol, comes from animal sources and is the form your skin produces. Most experts consider vitamin D3 more effective at raising and maintaining vitamin D levels in your blood.

Taking vitamin D supplements can help prevent deficiency in people who have limited sun exposure. This includes older adults, people with darker skin, and those who live in northern climates. Your healthcare provider can test your vitamin D levels to determine if you need supplementation.

Common uses

  • Preventing and treating vitamin D deficiency
  • Supporting bone health and preventing osteoporosis
  • Helping your body absorb calcium from food
  • Reducing risk of falls and fractures in older adults
  • Supporting immune system function
  • Treating rickets in children and osteomalacia in adults
  • Supporting mood and mental health

How it works

Vitamin D works by helping your intestines absorb calcium and phosphorus from the food you eat. Without enough vitamin D, your body cannot absorb calcium properly, even if you eat calcium-rich foods. Your kidneys convert vitamin D into its active form called calcitriol. This active form tells your intestines to increase calcium absorption and helps maintain the right balance of calcium and phosphorus in your blood.

Vitamin D also plays important roles beyond bone health. It helps regulate your immune system, supports muscle function, and influences hundreds of genes throughout your body. Your parathyroid glands use vitamin D signals to control calcium levels in your blood. When vitamin D levels are low, your parathyroid hormone, or PTH, rises to pull calcium from your bones.

Dosage information

Most adults take between 600 and 2,000 IU of vitamin D daily. The recommended dietary allowance is 600 IU for adults under 70 and 800 IU for adults over 70. However, many healthcare providers recommend higher doses of 1,000 to 2,000 IU daily to maintain healthy blood levels. People with vitamin D deficiency may need higher doses of 5,000 to 10,000 IU daily for 8 to 12 weeks under medical supervision. Always take vitamin D with a meal containing fat for better absorption. Your doctor can determine the right dose for you based on your blood test results.

Side effects

  • Nausea or vomiting
  • Loss of appetite
  • Constipation
  • Weakness or fatigue
  • Headache
  • Dry mouth or metallic taste

Taking too much vitamin D over time can cause serious problems. High doses can lead to vitamin D toxicity with symptoms including confusion, kidney stones, irregular heartbeat, and high calcium levels. Stop taking vitamin D and contact your healthcare provider if you experience severe nausea, vomiting, confusion, or extreme thirst. Most side effects occur only with very high doses above 10,000 IU daily taken for extended periods.

Drug interactions

  • Corticosteroids like prednisone can reduce calcium absorption and weaken bones
  • Weight loss medications like orlistat can reduce vitamin D absorption
  • Cholesterol medications like cholestyramine can reduce vitamin D absorption
  • Seizure medications like phenytoin can increase vitamin D breakdown
  • Thiazide diuretics combined with vitamin D may cause high calcium levels
  • Avoid taking vitamin D with aluminum-containing antacids for long periods
  • Do not take high doses of vitamin D if you have high calcium levels or kidney disease

Blood test monitoring

Regular blood testing helps ensure your vitamin D levels stay in the healthy range. Rite Aid offers blood testing that measures vitamin D, calcium, and parathyroid hormone, or PTH. Your vitamin D level should typically be above 30 ng/mL for good bone health. Testing every 3 to 6 months makes sense when starting supplementation or adjusting your dose. Once your levels are stable, annual testing is usually enough. Checking calcium levels prevents you from taking too much vitamin D, which can cause dangerously high calcium. PTH testing shows how well your parathyroid glands are responding to vitamin D.

Related blood tests

Calcium

Calcium, Serum

  • Reveal bone health issues effortlessly
  • Detect calcium imbalances early
  • Clarify muscle weakness causes quickly
$99

Comprehensive Metabolic Profile (includes eGFR)

  • Reveal underlying health conditions effortlessly
  • Pinpoint the cause of chronic fatigue
  • Assess your cardiovascular health comprehensively
$99

Kidney Function Profile

  • Reveal how well your kidneys are working
  • Detect early signs of kidney issues
  • Clarify the cause of your fatigue
$99

Frequently asked questions

The only way to know for sure is through blood testing. Many people have low vitamin D levels without obvious symptoms. Risk factors include limited sun exposure, darker skin, older age, obesity, and living in northern climates. Rite Aid offers blood testing that measures your vitamin D level along with over 200 other biomarkers.

Most experts recommend vitamin D3 because it raises and maintains blood levels more effectively than D2. Vitamin D3 is the same form your skin produces from sunlight. Both forms work in your body, but D3 typically requires lower doses to achieve the same blood levels.

Take vitamin D with your largest meal of the day for best absorption. Vitamin D is fat-soluble, meaning it absorbs better when taken with food containing fat. Morning or evening dosing works equally well. Choose a time you can remember consistently.

Most people cannot rely on sunlight alone year-round. Your skin makes less vitamin D in winter, at northern latitudes, through sunscreen, and with darker skin pigmentation. People over 50 also produce less vitamin D from sun exposure. Supplementation offers a reliable way to maintain healthy levels.

Your vitamin D blood level typically rises within 2 to 3 months of daily supplementation. People with severe deficiency may need 8 to 12 weeks of higher doses to reach healthy levels. Testing your levels after 3 months helps determine if your dose is working or needs adjustment.

Yes, taking extremely high doses over time can cause vitamin D toxicity. This typically requires doses above 10,000 IU daily for many months. Symptoms include nausea, weakness, kidney problems, and dangerously high calcium levels. Staying below 4,000 IU daily is considered safe for most adults without medical supervision.

Vitamin D and calcium work together for bone health. Vitamin D helps your body absorb calcium from food. If your diet lacks calcium-rich foods, taking a calcium supplement with vitamin D makes sense. However, getting calcium from food sources like dairy, leafy greens, and fortified foods is ideal.

Parathyroid hormone, or PTH, rises when your vitamin D or calcium levels drop too low. High PTH causes your body to pull calcium from your bones, weakening them over time. Checking PTH along with vitamin D and calcium gives a complete picture of your bone health.

Some research suggests vitamin D may support mood and mental health. Low vitamin D levels are common in people with depression. However, evidence that supplementation treats depression remains mixed. Maintaining healthy vitamin D levels supports overall wellness, including brain function.

Yes, vitamin D supplements are available over-the-counter at Rite Aid in various strengths. Common doses include 1,000 IU, 2,000 IU, and 5,000 IU. Rite Aid pharmacists can help you choose the right strength and answer questions about usage and interactions with your other medications.

Related health conditions

Osteoporosis Vitamin D Deficiency

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