What Are the Side Effects of Vitamin D?

Medically Reviewed by Minesh Khatri, MD on May 14, 2023
Written by WebMD Editorial Contributors
4 min read

‌Vitamins are important to your body’s health. The vitamins in your food, that you absorb from your environment, or get from supplements all work together. However, too much of certain vitamins can actually damage instead of help your well-being.

Vitamin D is a vitamin produced by your skin. Your skin absorbs sunlight, converts it into vitamin D, and uses it to help:

  • Keep your bones healthy 
  • Absorb calcium 
  • Improve the function of your parathyroid glands 
  • Prevent other conditions

You can get vitamin D from three main sources: sunlight, food, and supplements. 

Sunlight. Around 15 to 20 minutes of sunlight every few days is typically enough to provide you with a healthy level of vitamin D. The ultraviolet B (UV-B) radiation emitted by the sun is absorbed by your skin and turned into vitamin D. How you access sunlight affects how much vitamin D you have in the following ways:

  • Location: Locations farther from the equator don’t receive as much UV-B light. Locations closer to the equator have higher UV-B light levels.
  • Season: Certain locations, especially those farther from the equator, aren’t touched by UV-B light during cold seasons.
  • Time: Depending on the time of day, particularly between 10 a.m. and 3 p.m., sunlight is rich with UV-B. 
  • Melanin content: Generally, the darker your skin and the more melanin in it, the more sun exposure you need to get enough vitamin D. 
  • Environmental conditions: Areas with lots of cloud coverage or air pollution block UV-B light. 

Food. Certain foods have been fortified with extra vitamin D, primarily dairy products like milk and yogurt. Fish, orange juice, and eggs also contain some vitamin D. However, few foods naturally contain enough vitamin D to be your only source of it.

Supplements. The last line of defense for getting enough vitamin D is vitamin supplements. Supplements are usually only recommended in cases of vitamin D deficiency, for the prevention of other conditions, or if you don’t have consistent access to sunlight or foods with vitamin D.

Certain medical conditions, lifestyle, genetic factors, and medications can lead to a vitamin D deficiency.

While generally, vitamin D deficiency is asymptomatic, several typical signs  include:

  • Fatigue and exhaustion
  • Bone pain
  • Muscle weakness, aches, or cramps
  • Mood or behavior changes (such as symptoms of depression)

Certain medical conditions or operations that affect your vitamin D levels are:

In addition to where you live and your skin color, your age and weight can also affect your ability to produce and use vitamin D. 

Age. As you get older, your skin produces less vitamin D. For example, when you’re 65 years old or older, you will produce around 25% less vitamin D than when you're 25.

Weight. The more fat your body has, the more energy and vitamins are being stored in that fat. Keeping the vitamins stored means they're not being circulated and used throughout your body.

The following medications may lower your vitamin D levels:

Vitamin D supplements may be prescribed to prevent or protect against certain conditions in the following ways:

  • To protect against osteoporosis, rickets, osteomalacia, and other bone disorder
  • To reduce the risk of injury for people who are a fall risk
  • To prevent parathyroid problems

Types of supplements. Vitamin D comes in many multivitamins and on its own as an individual supplement. It comes in a variety of forms like soft gels, capsules, and liquids. It also comes in strengths from 50 to 1,000 IU and higher doses when prescribed by your doctor. Using the proper dosage is important to prevent vitamin D toxicity. 

Vitamin D toxicity is rare but can lead to a host of symptoms and complications. 

How much is too much? The amount of vitamin D you need is dependent on the factors described previously. For adults, the maximum amount of vitamin D you should take according to the National Institutes of Health is 4,000 IU. For children, the amount is less, depending on their age.

Signs of vitamin D toxicity are:

  • Nausea
  • Thirst 
  • Frequent urination
  • Constipation
  • Weakness
  • Confusion

Some side effects include:

  • Metal taste
  • Lack of appetite
  • Bone aches
  • Weight loss
  • Exhaustion or fatigue
  • Sore eyes
  • Itching
  • Vomiting

Vitamin D toxicity typically only results from taking a high dosage of supplements. Vitamin D from food and sunlight won’t cause vitamin D toxicity.

Reactions with other medications. Vitamin D supplements may react negatively with other supplements or medications. Consult with your doctor before taking vitamin D supplements to see how they will interact with your current medications, particularly:

  • Medications containing aluminum
  • Anticonvulsants
  • Atorvastatin, cholestyramine, or other cholesterol-lowering drugs
  • Calcipotriene
  • Digoxin
  • Diltiazem, verapamil, thiazide diuretics, or other blood pressure drugs
  • Orlistat
  • Steroids
  • Laxatives