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Signs of Vitamin D overdose: what to look out for

Updated on: July 1, 2021
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Vitamin D is a fat-soluble molecule that belongs to the same family as vitamins A, E, and K. It has several critical functions in the human body. Having too much (or too little) can have adverse effects, as we shall learn in this article.

Importance of Vitamin D

Vitamin D has several critical functions. It regulates the absorption of phosphorous and calcium and facilitates optimal immune response.  Optimal amounts of vitamin D will also promote normal growth and development of the bones and teeth.

Sources of vitamin D

 There are two ways to get vitamin D. first is from the sun, which will be covered later on. The next is from food. Vitamin D rich foods include:

  • Beef liver
  • Egg yolks
  • Cheese.
  • Fatty fish like mackerel, tuna, and salmon.
  • Vitamin D fortified foods like orange juice, dairy, cereals, and soy milk


  1. Salmon is one of the richest food sources of vitamin D. Three ounces of cooked salmon contain as much as 570 international units.
  2. You may also get vitamin D from supplements. However, it is advised that you consult your doctor on the appropriate dosage before you do 

Vitamin D and the sun

Your body produces vitamin D whenever it’s in the sun. The skin’s tissues start creating the substance the moment they’re exposed to the sun’s ultraviolet B rays. Several factors affect this process. They include

Time of day

The skin makes the most vitamin D when exposed to the sun at its highest point in the sky. 

Exposed surface area

Exposing more of your skin gives your body the chance to make more vitamin D.


People with light skin tones are better able to absorb vitamin D than those with darker complexions. They have more melanin, the compound which helps defend against skin cancer and sunburn. Research suggests that people with dark complexions may need between 30 minutes and 3 hours to get enough vitamin D, in contrast to lighter-skinned individuals.


Your location has a significant impact on how much vitamin D you can get from sunlight exposure. The sun's intensity reduces as one moves farther away from the equator. This means people living in the tropics get less sunlight than those living at the equator, limiting the amount of vitamin D their bodies can create. 

In the U.S., people living in the sunny south can meet their vitamin D needs much faster than those in the north.

Signs of Vitamin D overdose


HIgh doses of vitamin D can cause dangerous amounts of calcium to build up in your circulatory system, a condition known as hypercalcemia.  It occurs when your blood serum calcium levels are two standard deviations above average. 

Normal calcium levels lie between 8.8 and 10.8mg/dl. Hypercalcemia patients typically present with blood calcium levels between 14.0 and 16.0 mg/dl. Some signs of this may include constipation, reduced appetite, headaches, memory problems, tiredness, and thirst.

Frequent urination 

If you take too much vitamin D, it will increase the calcium levels in your blood. This may manifest as frequent urination accompanied by other signs like nausea, vomiting, and others. 

Kidney problems

Left untreated, hyperkalemia resulting from vitamin D toxicity may cause kidney problems and kidney damage. Too much vitamin D increases calcium absorption, which often leads to the formation of kidney stones.

Unfortunately, the condition can get worse. Studies suggest that vitamin D toxicity may lead to severe long-term kidney damage. Calcium deposits in the kidneys may cause nephrocalcinosis, which can lead to permanent kidney damage or failure.

The toxicity levels that would cause this condition are far above what you'd get from basking in the sun or consuming vitamin D-rich foods, so there is not much cause for concern if your health routine includes any of those activities. However, you are at significant risk if you frequently have large doses of vitamin D supplements.

Bone problems

Modest amounts of Vitamin D are good for bone health. But, too much will have the opposite effect, especially if it's against medical advice. Studies suggest that excessive vitamin D levels will interfere with the action of Vitamin K2, which facilitates the absorption of calcium for bone growth.

Signs of Vitamin D deficiency

Frequent sickness

Vitamin D keeps your immune system active so your body can fight off disease-causing viruses and bacteria. Studies have shown a correlation between deficiency and respiratory tract illnesses like bronchitis, colds, and pneumonia.

If you fall sick often, especially with the flu, you might have low vitamin D levels.

Tiredness and fatigue

This may come as a surprise, but vitamin D deficiency can cause fatigue or tiredness. In fact, it is associated with several other related symptoms like weakness, depression, and reduced cognitive performance. If you're experiencing any of these issues but don’t have preexisting physical or mental health problems, vitamin D deficiency could be the cause.

Bone pain

Vitamin D intake impacts skeletal health. Low levels may lead to musculoskeletal problems like bone pain, low bone mass, and fractures, which may be diagnosed as myopathy, osteolalacia, and osteoporosis.

Problems with wound healing

Vitamin D helps your body repair itself after injury. It controls the genes that regulate cathelicidin, an antimicrobial peptide the body uses to manage wound infections. This system is compromised when your body doesn’t have enough vitamin D, leaving it vulnerable to harmful microorganisms that slow the healing process.


There is a significant link between vitamin D deficiency and depression, as earlier mentioned. Most people suffering this condition also suffer low levels of vitamin D. This implies that it plays a vital role in brain function.

How much vitamin D is too much?

It depends on your age. The recommended daily intake varies by age group, as shown below. In a few circumstances, your healthcare provider may recommend lower or higher doses than your recommended intake.

  • Babies (0-6 months): 400 IU per day
  • Babies (6-12 months): 400 IU per day
  • Children (1-3 years) years: 600 IU per day
  •  Children (4-8): 600 IU per day
  •  Children, adolescents, and adults (9-70): 600 IU per day
  •  Pregnant women or lactating mothers between 14-50 years old: 600 IU


The recommended amounts are expressed in International units (IU). The International unit (IU) is the quantity of a substance, like a hormone, vitamin, or toxin that produces a specific effect when evaluated according to internationally recognized biological procedures.

If you're consuming vitamin D as a dietary supplement, the label will list the amounts each pill contains, either in micrograms or International units.Sometimes, the amounts won’t be listed directly, but they will still provide a daily percentage value. It will show the amount of vitamin D within each serving as a percentage of 800 UI.  You may also obtain estimates of the Vitamin D levels in various foods by consulting the National Institute of Health's guidance page.

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