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Vitamin D deficiency

Dr Karen Martin
Reviewed by Dr Karen MartinReviewed on 19.10.2023 | 4 minutes read

Vitamin D is essential for your body to form strong bones and teeth, along with many other benefits. It helps your gut absorb calcium and phosphate, which form part of your bones. It also helps muscles function correctly and can help boost your immune system.

If you do not get enough vitamin D, you may have no symptoms at first, or you might just feel a bit tired and achy. As vitamin D deficiency becomes severe or prolonged, bone pain or bone deformities can develop. For children, over time, the long leg bones can permanently bend, making the legs look bowed, in a condition known as rickets. Bones are already set in adults, but prolonged severe vitamin D deficiency can cause osteomalacia, where sufferers complain of bone pain and muscle weakness. This is different to osteoporosis which is a condition characterized by a decrease in bone mass and density, leading to bones becoming fragile and more prone to fractures, whereas osteomalacia is a condition characterized by softening of the bones due to a deficiency of vitamin D or problems with its metabolism. This leads to impaired mineralization of the bone matrix.

Who gets vitamin D deficiency?

Your skin is the great vitamin D factory, using direct sunlight to convert it to a useful form in the body. To a lesser extent, certain foods contain vitamin D, such as oily fish, egg yolk, red meat, and some cereals and margarine, where they artificially add vitamin D.

Unfortunately, both of these sources have pitfalls. There is not enough sunshine in the winter months in northern countries such as the US. And dietary sources provide only a small amount of the vitamin D we need to keep us in tip-top health. That’s where supplements are essential, especially between October and April.

In this case, take what is called a maintenance dose from October through April, which is 10 micrograms daily (or 400 international units), or it can be taken in a higher weekly dose.

Some people are at greater risk of vitamin D deficiency, either through lack of exposure to sun or genetics/aging causing a lack of ability to convert vitamin D, and should therefore take supplements all year round. These include those who don’t get outdoors much, or cover their face and neck when they go out, and the elderly. Those from Asian, African, or Caribbean backgrounds should take the same amount all year round, as darker skin prevents the skin from producing vitamin D from sunshine as efficiently.

Pregnant and breastfeeding women and children have higher vitamin D requirements, so are therefore more likely to be deficient. A vegan diet is lower in vitamin D, given the avoidance of foods that naturally contain it.

Healthwords pharmacists' top tips

Vitamin D supplements are available at the pharmacy or health food stores, and they usually come in a version called vitamin D3, or cholecalciferol. You can buy this on its own or combined with other vitamins such as calcium, or in multivitamins.

If you are in a high-risk group or for anyone living in the US in winter, you do not need to check vitamin D levels, you can just start taking supplements. If you are worried, you can get your levels checked in a blood test at your doctor’s office.

Vitamin D comes as tablets, capsules, oral sprays, or oral liquids. You can take it daily or at a higher dose weekly. It comes in a variety of strengths, depending on your personal needs:

  • 10 mcg (or 400 IU) for children over 4 years old
  • 20-25 mcg (800-1000 IU) for women during pregnancy
  • 25 mcg (1000 IU) for general year-round maintenance
  • 50-100 mcg (2000-4000 IU) preparations for those at-risk groups with severe deficiencies, such as the elderly, those with darker skin, vegans or those with dietary restrictions, and those who may be housebound or have little opportunity to get good sunlight during spring and summer

Vitamin D can be combined with calcium, where they work together to be properly absorbed and maintain healthy, strong bones and teeth. In combination with vitamin K, it can help maintain a healthy circulation, as it mops up excess calcium in the bloodstream, which prevents it from forming plaques to block arteries.

Vitamin D is a fat-soluble vitamin, which means that you maximize absorption by taking it with healthy fats such as avocados, nuts, seeds, eggs, or a dressing made with olive oil.

Am I fit for work?

You are likely to be fit for work if you have vitamin D deficiency.

When should I see my doctor?

Vitamin D is considered safe for most. Certain medications may mean you need to check with your doctor before starting them. These include digoxin or so-called water tablets, or diuretics, such as bendroflumethiazide, bumetanide, indapamide, and spironolactone.

You can speak to your local pharmacist or book a routine visit with your doctor if you are concerned that you have vitamin D deficiency or have any symptoms.

The doctor will ask you about your past medical history, any current symptoms, and any risk factors for vitamin D deficiency. They may do a general examination and take a blood test. If you have severe vitamin D deficiency, they will prescribe vitamin D supplementation; this will be a higher amount than people who are taking vitamin D for maintenance in the winter months.

If this level is just lower than normal (‘vitamin D insufficiency’), or it is the winter months, or you are in a group that is higher risk, your doctor will not prescribe the higher dose and suggest you just buy supplements yourself.

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This article has been written by UK-based doctors and pharmacists, so some advice may not apply to US users and some suggested treatments may not be available. For more information, please see our T&Cs.
Dr Karen Martin
Reviewed by Dr Karen Martin
Reviewed on 19.10.2023
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