Vitamin D Side Effects – Deficiency and Overdose

Alpa Momaya

May 10, 2023

Vitamin D constitutes one of the most important fundamentals for maintaining overall health.

Vitamin D is a fat-soluble vitamin that promotes calcium absorption, regulates bone growth and muscular rigidity, and plays a role in immune function. However, getting adequate amounts of this vitamin from your diet alone may be difficult, as rich natural sources are rare.

For these reasons, it’s common for people not to get enough vitamin D. Both Excess of Vitamin D and deficiency can lead to side effects and health issues explained in this article.

Your skin produces vitamin D on exposure to sunlight. However, if you spend most of your time indoors or live at a high latitude, you’ll need to get this vitamin from your diet. Good dietary sources include fatty fish, fish oils, egg yolk, liver, mushrooms.

Vitamin D Types and Uses

It exists in two primary forms:

  • Vitamin D2 (ergocalciferol)
  • Vitamin D3 (cholecalciferol)

The primary source of Vitamin D is sunlight. Our skin makes vitamin D3 on exposure to sunlight. Vitamin D3 can also be found in animal-sourced products while Vitamin D2 mainly comes from plant sources and fortified foods. 

Vitamin D is an essential constituent in regulating the balance of calcium and phosphorus in the body. It also helps in maintaining bone density and strong teeth. Vitamin D is useful in treating conditions like:

  • Hypophosphatemia
  • Hypoparathyroidism
  • Rickets
  • Brittle bones
  • Asthma
  • Hay fever

Vitamin D supplements are usually recommended for people over the age of 65 to prevent the decay of bones and other age-related complications. If you take vitamin D supplements, consider choosing Vitamin D3 because our bodies can absorb it more efficiently than vitamin D2. 

Under normal circumstances, the recommended daily allowance is 400–800 IU (10–20 micrograms), but standard supplemental doses range from 1,000–2,000 IU (25–50 micrograms) per day. Unless prescribed by a doctor, anything more could be harmful and detrimental to health.

Sources of Vitamin D

You can get vitamin D from natural resources, which you can substitute with artificial supplements. Some foods that contain vitamin D are:

  • Fatty fish such as sardine, tuna, and mackerel
  • Fortified cheese
  • Mushrooms
  • Egg yolks
  • Fortified milk
  • Fortified orange juice
  • Fortified yoghurt 

Causes Of Vitamin D Deficiency 

Vitamin D is a wonder nutrient, the lack of which can cause several health issues ranging from fatigue and frequent cold to grave ones like weak bones and depression. To prevent its deficiency we need to know its specific risk factors. 

Here’s a list of the causes of Vitamin D deficiency

 1. Lack of sunlight exposure

Vitamin D is also known as the ‘sunshine vitamin’ as according to research exposure to sunlight is necessary for our bodies to produce it. People living closer to the equator are bound to be more exposed to the sun, eventually leading to the production of Vitamin D in their bodies. Similarly, the ones living at higher latitudes see a lower production of the body. 

 2. Skin Colour

Research indicates that melanin, the pigment that gives skin its colour, reduces its ability to produce vitamin D. Thus, people with darker skin tones are more likely to suffer from Vitamin D deficiency. 

 3. Obesity

Vitamin D is a fat-soluble vitamin. Research has proved that vitamin D can get trapped between the fatty tissues and not be used for production by the body. This puts people with higher BMI at a greater risk to have Vitamin D deficiency. 

 4. Age

Our skin becomes less efficient at producing vitamin D as we age as proved by this study. Furthermore, our kidneys too start to lose their efficiency at converting Vitamin D to its active form with age. Thus, older adults are increasingly susceptible to vitamin D deficiency.

 5. Medical conditions

People suffering from celiac disease, IBD, cystic fibrosis and those who have had gastric bypass surgery or parts of their intestines removed face difficulty in absorbing Vitamin D from food. 

6. Medications

Certain medications, such as glucocorticoids, anticonvulsants, and antiretroviral drugs, can interfere with the body’s ability to use vitamin D.

Vitamin D Deficiency Side-effects

A Vitamin D deficiency isn’t easy to diagnose, as it doesn’t always cause symptoms until levels become very low or have been low for some time. But some of the more alarming signs to watch out for include:

 1. Decreased Bone Density

The body absorbs calcium with the help of Vitamin D and thus the lack of calcium results in low bone density. Weak bones can lead to osteoporosis, and the loss of bone density, which can lead to fractures. 

According to Bone Health & Osteoporosis Organisation, Vitamin D plays a very crucial role for women during menopause wherein bone density decreases increasing the risk for osteoporosis.

 2. Reduces Immunity

Research confirms that a deficiency in vitamin D is associated with increased autoimmunity and increased susceptibility to infection.

Lack of vitamin D increases inflammation and lowers immunity. It also results in an increased heart rate and is a prime reason for diabetes.

In addition, the reduction in immunity may cause diseases such as multiple sclerosis and other infections. It weakens the body from within and prevents natural disease-fighting capacities. 

 3. Affects Mental Health

Studies have proved that Vitamin D deficiency has a direct correlation with poor mental health. Serotonin, the brain hormone associated with mood elevation, falls with decreased sun exposure resulting in a lack of Vitamin D.

Another way to look at it is that people who spend more time indoors lack Vitamin D and are more likely to have a strained social life. The lack of a social circle discourages them to go out and this, in turn, ties them into a degenerative cycle.

Vitamin D Overdose

A blood test is the best way to determine what your current levels of Vitamin D are. The reference range in your report will help your physician determine the result and course of action.

While Vitamin D is usually considered safe during pregnancy and breastfeeding, the recommended amount is under 4000 IU. You should avoid a higher dosage to prevent complications.

In the case of children, vitamin D is considered safe if taken orally in quantity as prescribed by a doctor. However, prolonged use of vitamin D may lead to specific health issues in children. Therefore, children between the ages of 1-3 years should not be given a dosage over 2500 IU and between 4-8 should not have a dosage over 3000 IU. These may otherwise lead to complications such as:

  • Atherosclerosis (hardening of the arteries)
  • Histoplasmosis (Fungal infection)
  • Hypercalcemia 

Vitamin D Overdose Signs

  • Unexplained exhaustion
  • Loss of appetite and weight loss
  • Constipation
  • Dry mouth
  • Changes in skin turgor (Skin that is slow to return to normal after being pinched)
  • Increased thirst and frequency of urination
  • Continuous headaches
  • Nausea
  • Reduced reflexes
  • Confusion, disorientation, or trouble thinking
  • An irregular heartbeat
  • Muscle weakness and reduced muscle tone
  • Changes in gait

Excess vitamin D can have adverse impacts on the physiology of an individual. Recurrent toxicity caused by excessive vitamin D has been a known cause for the following problems:

  • Extreme dehydration
  • High blood pressure
  • Trouble breathing
  • Frequent loss of consciousness
  • Kidney stones
  • Tinnitus (ringing in the ears)
  • Pancreatitis (inflammation of the pancreas)
  • Gastric ulcers

In worst cases, extreme and chronic vitamin D toxicity can cause abnormal heart rhythm and kidney failure. It can even lead to hearing loss. 

Potential Side Effects of Vitamin D Overdose

Although the body needs a stable dose of vitamin D, overdosage can negatively impact physical and psychological health. An overdosage of vitamin D may result in the following problems:

 1. Hypercalcemia

Elevated levels of vitamin D in the body can cause the intestines to absorb excess  amounts of calcium and release it into the body. This leads to a condition called hypercalcemia.

To put it simply, hypercalcemia occurs when the calcium density in the blood increases above the healthy limit. This excess calcium density can lead to the following problems and symptoms:

  • Loss of appetite
  • Diarrhoea
  • Unexplained exhaustion
  • High blood pressure
  • Muscle weakness
  • Dehydration
  • Increased thirst 
  • Frequent urination
  • Irregular heartbeat
  • Reduced reflexes
  • A metallic taste in the mouth 
  • Dry and sunken eyes

2. Dehydration

Elevated calcium levels in the blood cause dehydration. It can result in polyuria or irregularly large quantities of urine. When a person passes excessive urine, he loses a considerable amount of water and electrolytes. As a result, they might be prone to dehydration.

While the exact reason is unknown, one of the reasons could be an increase in antidiuretic hormones which creates more significant quantities of urine. The symptoms of moderate dehydration include:

  • Increased thirst
  • Irritability
  • Sunken eyes
  • Dry eyes
  • Restlessness

However, severe dehydration is life-threatening. The symptoms are:

  • A weak or absent pulse
  • Low blood pressure
  • Unexplained exhaustion
  • Very little or no urine output
  • Unconsciousness

3Kidney Damage

Kidney damage is another major problem caused by excess vitamin D. Hypercalcemia may form small cysts in the body that can cause organ damage and organ failure. In addition, when calcium gets stuck in the kidney tissues, it causes nephrocalcinosis. A study conducted in 2015 shows that it results from vitamin D3 toxicity in the body. The symptoms include:

  • Fever
  • Severe pain in the groin and sides of the back
  • Nausea and vomiting

4. Heart Issues 

As per a 2012 case study, high calcium content in the blood can reduce the ability of the heart cells to perform. This leads to calcium and phosphate deposition in heart valves and arteries.  Hypercalcemia can cause palpitations, fainting episodes and abnormal heart rhythm

 5. Lung Damage

Vitamin D deficiency has been established by research as exceedingly prevalent in many chronic lung disease populations. High calcium density in the blood causes crystals to deposit in soft organs like the lungs. These calcium deposits, also known as ectopic concentrations, impair the organ’s functioning. The symptoms include:

  • Chest pain
  • Trouble breathing
  • Coughing

6. Psychological Impacts

Several studies have shown a direct relationship between the excessive dosage of vitamin D supplements and anxiety.

Research demonstrates that since there is a direct link between depression and anxiety, vitamin D overdose may lead to several neurological disorders such as:

  • Dementia
  • Parkinson’s disease
  • Multiple sclerosis
  • Epilepsy
  • Schizophrenia

HealthifyMe Suggestion

Vitamin D deficiency is highly prevalent and there is a better understanding of the various benefits of  adequate vitamin D levels.  Natural sources such as sunlight and vitamin D-rich foods are the best ways to get adequate vitamin D.  However if you have severe vitamin D deficiency, you can consider supplementation after talking to a physician.


Like all micronutrients, Vitamin D is necessary for our body’s efficient functioning and thus any unfavourable rise or fall in its level can cause health complications. 

Given today’s lifestyle, Vitamin D deficiency among the population has spiked up significantly. People spend most of their time indoors which prevents their skin from getting adequate sunlight. Although Vitamin D supplements are available as over-the-counter drugs, it’s recommended to maintain its levels through natural sources like sunlight and food. Spending 20 mins under the sun during the early morning is an excellent way to maintain the optimum level of Vitamin D in your body. 

Disclaimer: The purpose of this article is just to disperse knowledge and raise awareness. It does not intend to replace medical advice from professionals. For further information please contact our certified nutritionists Here

Reference Sources 

  1. Vitamin D: The “sunshine” vitamin:
  1. Skin color is relevant to vitamin D synthesis:
  2. Vitamin D Deficiency: Consequence or Cause of Obesity?:,increased%20in%20obesity%20%5B6%5D.
  1. Vitamin D and Aging:
  1. What Women Need to Know:
  1. Vitamin D and the Immune System:
  1. Vitamin D deficiency and psychological disorders:
  1. Vitamin D deficiency and chronic lung disease:
  1. Vitamin D: The Connection to Depression and Anxiety:,anxiety%20as%20well%20as%20depression.
  1. Vitamin D and Neurological Diseases: An Endocrine View:

Frequently Asked Questions (FAQs)

Q. How much vitamin D is too much?

A. If you consume less than 100mg of vitamin D per day, it is considered normal. Anything more may lead to body ailments such as hypercalcemia and kidney or lung damage due to excessive calcium concentration in the blood.

Q. Are there any side effects of taking Vitamin D?

A. Yes, there are several side effects of taking vitamin D in excess. Less than 100mg of vitamin D per day is a standard dosage. However, prolonged use of vitamin D supplements can lead to a steady increase of calcium content in the blood. It may cause several ailments like hypercalcemia and lung or kidney damage.

Q. How much vitamin D can you take in one day?

A. Approximately 100 milligrams of vitamin D is a normal dosage. Usually, organic food and the sun are considered the best sources of Vitamin D in the human body. You should only take supplements after consultation with a physician.

Q. What drugs should not be taken with Vitamin D?

A. You should not take the following drugs with vitamin D supplements:
Phenobarbital and phenytoin, which can treat epilepsy
Orlistat, a weight loss medication
Cholestyramine, which can reduce cholesterol

Q. Can a lack of vitamin D cause weight gain?

A. The lack of vitamin D can cause both weight gain and weight loss. In addition, depending on the person’s physiology, it can trigger hormonal changes that may result in increased or decreased appetite, indirectly triggering the weight gain or loss process.

Q. Can vitamin D deficiency make you sick?

A. Yes, vitamin D deficiency can make you sick since it triggers temporal and hormonal changes. It also affects the lungs and kidneys as well as cause cognitive impairments in adults, which can make you sick.

Q. What happens if your vitamin D is low?

A. A deficiency of vitamin D causes behavioural changes along with the following:
Muscle Weakness
Bone pain

Q. Can low vitamin D cause neurological symptoms?

A. Yes, low vitamin D can cause several neurological symptoms such as depression and anxiety. It may also cause dementia, Parkinson’s disease, multiple sclerosis, epilepsy and schizophrenia.

Q. Can vitamin D deficiency make you sick?

A. Yes, vitamin D deficiency can make you sick since it triggers temporal and hormonal changes. It also affects the lungs and kidneys as well as cause cognitive impairments in adults, which can make you sick.

Q. Can vitamin D deficiency cause anxiety?

A. Yes, Vitamin D deficiency can cause anxiety because it has psychological impacts. It has a direct interlink between depression and anxiety.

Q. Can vitamin D cause cognitive impairment?

A. Yes, a deficiency in vitamin D can lead to cognitive impairment. However, this is usually treatable. In addition, an increased intake of vitamin D usually leads to problems that resolve after some time.

By: Alpa Momaya, Post Graduate Diploma in Dietetics

Medically Reviewed By: Sumita Thomas, Masters in Dietetics and Clinical Nutrition Services

About the Author

As the holder of a Post Graduate Diploma in Dietetics from the University of Mumbai, Alpa Momaya has always understood the value of good nutrition in an individual's life. She is a Registered Nutritional Practitioner (Canada) with over 15 years of experience in the field. Specializing in Clinical Nutrition, Pre & Post Natal Diets, and Weight Management, Alpa found her calling as a Sr. Nutritionist with HealthifyMe. Alpa's love for cooking and good nutrition has seen her contribute several recipes to the HealthifyMe database over the years. Additionally, she takes a keen interest in reading and painting.

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