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What happens if I take too much Vitamin D?

What happens if I take too much Vitamin D?

Stefano Mirabello NowPatientGreen tick
Written by Rajive Patel, BPharm
Updated on 31 Aug 2023

Most people think of vitamin D as the “sunshine vitamin” because our bodies produce it in response to sun exposure. However, vitamin D is also found in some foods, such as oily fish and it’s available as a supplement. Even though our bodies need only a small amount of vitamin D, this essential nutrient plays a vital role in many body functions.

Vitamin D deficiency is relatively common, especially during winter when there is less sunlight. Vitamin D deficiency can cause several health problems, so it’s essential to be aware of the symptoms and get treatment if needed. Take a closer look at vitamin D deficiency causes, symptoms and treatment options.

Why do we need Vitamin D?

Vitamin D is an essential nutrient that plays a role in many different body functions:

  • It helps the body absorb calcium and phosphate from the diet, which is essential for healthy bones and teeth
  • It helps to regulate calcium levels in the blood, preventing calcium deposits from forming in the arteries and other tissues
  • It plays a role in the immune system, helping to fight off infections and keeping the body healthy

How much vitamin D do I need?

According to the NHS, the recommended daily amount (RDA) of vitamin D is:

  • 10 micrograms of vitamin D a day for children from the age of 1 year to adults. This includes pregnant, breastfeeding women and people at a higher risk of vitamin D deficiency
  • 8.5 to 10 micrograms of vitamin D a day for babies up to the age of 1 year

Sometimes the amount of vitamin D is expressed as International Units (IU). 1 microgram of vitamin D is equal to 40 IU. So 10 micrograms of vitamin D is equivalent to 400 IU.

What are the causes of Vitamin D Deficiency?

There are several reasons why people might not get enough vitamin D. For example:

Spending too much time indoors

Our bodies produce vitamin D when our skin is exposed to sunlight. Ultraviolet B (UVB) rays from the sun interact with a fat-soluble vitamin D precursor in the skin, starting a chemical reaction that ultimately produces vitamin D3. This vitamin D3 is then transported to the liver and converted into 25-hydroxyvitamin D3. Finally, this form of vitamin D3 moves to the kidneys, where it is turned into the active form of vitamin D that our bodies need for bone health. Although we can also get vitamin D through certain foods, sunshine is still the best way to ensure that our bodies have enough of this important nutrient.

People who spend most of their time indoors are at risk for deficiency because they’re not getting enough sunlight. People who work indoors or live in northern climates are especially at risk for a deficiency, as they may not get enough sun exposure throughout the year. Older adults are especially vulnerable since they often spend less time outdoors.

Wearing sunscreen

Sunscreen is an important part of protecting your skin from the sun’s harmful rays and the risk of skin cancer. However, did you know that sunscreen can also affect your body’s ability to produce vitamin D? As we have already learned, the body produces vitamin D when exposed to sunlight. But when you wear sunscreen, it blocks the ultraviolet rays that help make vitamin D.

Sunscreen works by absorbing, reflecting or scattering UV rays, which can reduce the amount of UV radiation that reaches our skin. As a result, it can also reduce the amount of Vitamin D that our body can produce. So if you are someone who always wears sunscreen or spends a lot of time indoors, you may be at risk for vitamin D deficiency.

If you’re going to be spending time in the sun, choose a sunscreen with an SPF of 30 or lower for some protection while allowing your skin to still produce some Vitamin D.

Having dark skin

Not all skin tones are equally effective at producing Vitamin D. The darker the skin, the more melanin it contains. Melanin is a pigment that protects from the sun’s harmful UV rays. While this protection is beneficial in many ways, it also means that people with darker skin have a reduced ability to produce Vitamin D.

As a result, they may need to take supplements or increase their exposure to sunlight to maintain healthy levels of the vitamin.

Having certain health conditions

Some medical conditions can affect our body’s ability to produce this important nutrient. Crohn’s disease, celiac disease, and cystic fibrosis are all malabsorption disorders that can interfere with the absorption of nutrients from food, including vitamin D. Liver and kidney disease can also affect the body’s ability to metabolize vitamin D, making it difficult for the body to use this nutrient effectively. As a result, people with these medical conditions may be at risk of vitamin D deficiency.

Obesity and being overweight

Being overweight or obese can affect our body’s ability to produce Vitamin D. BMI (body mass index) can impact how much vitamin D our bodies make. People with higher BMIs tend to have low vitamin D levels. This is because fat cells store more vitamin D than lean tissue. The release of vitamin D from fat tissue is extremely slow.

So, if someone is overweight or obese, they may not be getting enough vitamin D even if they are spending time in the sun. This can lead to health problems such as osteoporosis, diabetes, and some cancers. If you are overweight or obese, talk to your doctor about whether you need to take a vitamin D supplement.

Taking certain medications

Some medications can affect our body’s ability to produce Vitamin D. For example, corticosteroids and anticonvulsants can reduce the amount of vitamin D that our bodies produce. In addition, some cholesterol-lowering medications can block the absorption of vitamin D.

If you are taking any of these medications, it is important to talk to your doctor about how to get enough vitamin D. They may recommend that you take a dietary supplement or expose yourself to more sunlight. Taking care of your vitamin D levels is an important part of maintaining your overall health.

Vitamin D Deficiency Symptoms

There are a few different symptoms of vitamin D deficiency. One common symptom is bone pain or muscle weakness. This can happen because vitamin D plays a role in calcium absorption and muscle function.

If you have a vitamin D deficiency, you may also notice that you’re constantly fatigued or having trouble sleeping. This is because vitamin D helps regulate sleep cycles.

Another symptom of a vitamin D deficiency is increased illnesses or infections. Vitamin D strengthens the immune system by fighting off bacteria and viruses. If you are prone to colds or other respiratory illnesses, a lack of vitamin D could be the reason why.

Finally, one telltale sign of a deficiency is depression or anxiety. While researchers aren’t quite sure why there’s a link between these mental health conditions and vitamin D deficiencies, they believe that it has something to do with how vitamin D affects brain function.

Most people with mild or moderate vitamin D deficiency don’t experience any symptoms because the lack of this nutrient isn’t usually severe enough to cause health problems. However, if left untreated, severe Vitamin D deficiency leads to an increased risk of many health complications such as:

  • Osteoporosis, also known as brittle bones
  • Osteomalacia, also known as Rickets (the bones become soft, resulting in bone deformities)
  • Cardiovascular disease
  • Type 2 diabetes
  • High blood pressure
  • Cognitive impairment (decline in thinking and memory skills)
  • Muscle weakness
  • Falls/fractures in older adults
  • Hair loss (Some studies have shown a link between low vitamin D levels and hair loss)

If you’re experiencing any of these symptoms, talk to your doctor about getting tested for vitamin D deficiency.

Vitamin D Deficiency Treatment

If you think you might have a vitamin D deficiency, the first step is to schedule an appointment with your doctor so they can perform some tests including a blood test called the 25-hydroxyvitamin D level test. This is the most common test used to measure the amount of vitamin D in the blood and is considered to be the most accurate way to determine whether someone is deficient in the nutrient.

If your levels are low, your doctor will likely recommend that you take supplements and spend more time outdoors to increase your levels of vitamin D. It’s essential to follow your doctor’s recommendations as untreated deficiencies can lead to more serious problems such as osteoporosis or even heart disease down the line.

Fortunately, most people who have low levels of vitamin D can increase their levels relatively easily with some lifestyle changes or supplements.

The best way to treat vitamin D deficiency is by getting more sunlight exposure or taking supplements containing vitamin D3 (cholecalciferol) or vitamin D2 (ergocalciferol).

The recommended daily allowance for vitamin D depends on your age. Your doctor can help you determine if you need to take supplements and how much you should take based on your test results and health history.

While exposure to sunlight is the best way to get vitamin D, certain foods can also help to improve vitamin D levels in the body. Foods that are good sources of vitamin D include egg yolks, fatty fish such as salmon, tuna, sardines and mackerel, cod liver oil, beef liver, dairy products such as milk, cheese and yoghurt; and fortified foods such as orange juice and cereals.

Is it harmful to take too much Vitamin D?

It is possible to have too much vitamin D in your system, causing a condition known as vitamin D toxicity. It usually results from taking supplements in excess. Symptoms of vitamin D toxicity can include nausea, vomiting, poor appetite, weight loss, fatigue and constipation. In more severe cases, vitamin D toxicity can lead to kidney damage and high levels of calcium in the blood, which can cause confusion and heart arrhythmias.

If you think you may be experiencing vitamin D toxicity, it is important to see a doctor as soon as possible so that they can perform a blood test and check your calcium levels. The main consequence of vitamin D toxicity is a buildup of calcium in your blood (hypercalcemia), which can cause nausea and vomiting, weakness and frequent urination.

Vitamin D plays an important role in many body functions but unfortunately, deficiency is relatively common, especially during winter months when there is less sunlight. Be aware of the symptoms so you can get treatment if needed; untreated deficiency can lead to some health complications. The best way to treat deficiency is by getting more sunlight exposure or taking vitamin D supplements containing vitamins D3 or D2.

Talk to your doctor if you think you might be deficient so they can test your levels and recommend appropriate treatment options. Always tell your healthcare provider about your medications and any supplements or herbal medication you take.


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NowPatient has taken all reasonable steps to ensure that all material is factually accurate, complete, and current. However, the knowledge and experience of a qualified healthcare professional should always be sought after instead of using the information in this page. Before taking any drug, you should always speak to your doctor or another qualified healthcare provider.

The information provided here about medications is subject to change and is not meant to include all uses, precautions, warnings, directions, drug interactions, allergic reactions, or negative effects. The absence of warnings or other information for a particular medication does not imply that the medication or medication combination is appropriate for all patients or for all possible purposes.

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