Common Causes of Vitamin D Deficiency in the Elderly

Abstract:
Older adults are more likely to have low vitamin D because the skin’s ability to synthesize vitamin D declines with age, many spend less time outdoors, and dietary intake may be low. Digestive conditions, kidney or liver problems, obesity, gastric bypass surgery and some medicines can also contribute to low vitamin D levels. ^[1–4]

Vitamin D helps the body absorb calcium and supports normal bone and muscle function. In older adults, low vitamin D can contribute to weak or fragile bones and may be associated with muscle weakness. Because symptoms of vitamin D deficiency can be subtle or absent, risk factors are often more useful than symptoms alone when deciding whether an older person should speak with a healthcare professional. ^[1][3]

What are the most common causes of vitamin D deficiency in older adults?

The causes often overlap. An older adult may have more than one risk factor at the same time, such as spending most days indoors, eating little vitamin D-rich food and living with a condition that affects absorption or vitamin D metabolism. ^[2–4]

Why does ageing reduce vitamin D production in the skin?

The skin makes vitamin D when it is exposed to ultraviolet B (UVB) radiation. With age, the skin becomes less efficient at this process. Older adults are also more likely to spend time indoors because of reduced mobility, illness, residential care or lifestyle changes. People with darker skin have more melanin, which also reduces vitamin D production from the same amount of sunlight. ^[2][3]

Sunlight can contribute to vitamin D status, but there is no single safe number of minutes that works for everyone. Skin tone, clothing, time of day, weather and other factors change how much vitamin D is produced. It is therefore better not to depend on intentional unprotected sun exposure as the only strategy; food and supplements, when appropriate, provide more predictable intake. ^[3]

Can a poor diet cause vitamin D deficiency in the elderly?

Yes. Vitamin D occurs naturally in relatively few foods, and older adults may eat less because of poor appetite, dental problems, swallowing difficulties, illness or restricted diets. Good sources include oily fish such as salmon, sardines and mackerel, egg yolk, and foods fortified with vitamin D where available. ^[3]

For some older adults, diet alone may not provide enough vitamin D. A healthcare professional such as a dietitian can help assess food intake and whether a supplement is appropriate. ^[3]

How do digestive conditions affect vitamin D absorption?

Vitamin D is fat soluble, so the intestine needs to absorb dietary fat normally for vitamin D to be absorbed well. Conditions such as celiac disease, Crohn’s disease and ulcerative colitis, as well as some liver disorders, can reduce absorption. Gastric bypass surgery can also increase the risk of low vitamin D. ^[3][4]

When malabsorption is present, simply taking a standard over-the-counter dose may not be enough. The underlying condition and the person’s vitamin D status should be reviewed by a healthcare professional. ^[3]

Can kidney or liver disease cause low vitamin D?

Yes. Vitamin D from food, supplements or skin production must be converted in the liver and then mainly in the kidneys before the body can use its active form. Chronic kidney disease can disrupt this process, and some liver conditions can also affect vitamin D status. ^[3][4]

People with kidney disease should not self-treat with high-dose vitamin D or prescription forms such as calcitriol. These treatments are used for specific indications and require medical supervision because calcium, phosphate, kidney function and other factors may need monitoring. ^[3][4]

Can medicines or other health factors contribute?

They can. The NIH lists obesity as a risk factor for lower circulating vitamin D, and some medicines can affect vitamin D metabolism or interact with vitamin D and calcium. Older adults often take several medicines, so a medication and supplement review is useful before starting a new vitamin D product. ^[3]

Bring a complete list of prescription medicines, over-the-counter products and supplements when speaking with a healthcare professional. This is especially important for people with kidney problems, high calcium levels, osteoporosis treatment or medicines that can alter calcium balance. ^[3]

How can older adults lower their risk of vitamin D deficiency?

A practical plan usually combines food, appropriate outdoor activity, and supplementation when needed. The right approach depends on diet, mobility, skin exposure, medical conditions, medicines and whether deficiency has already been diagnosed. ^[3][5][6]

• Include vitamin D-rich foods regularly, such as oily fish, eggs and fortified foods where suitable. ^[3]
• Avoid relying on a fixed “sun exposure prescription”. Vitamin D production varies widely, and sun protection remains important for skin health. ^[3]
• Ask a healthcare professional whether a vitamin D supplement is appropriate, especially if the person is homebound, has malabsorption, osteoporosis, kidney disease or other risk factors. ^[3][5]
• Do not use high-dose vitamin D for long periods without professional advice. Excessive supplemental vitamin D can cause high calcium levels and other serious problems. ^[3]

Malaysia context: The Malaysian Clinical Practice Guidelines for Management of Osteoporosis (3rd Edition, 2022) list 800 IU daily as the vitamin D intake for adults older than 65. This is not a universal treatment dose for every older adult; individual needs can differ. ^[5]

Should every older adult get a vitamin D blood test?

Not necessarily. A 25-hydroxyvitamin D [25(OH)D] blood test is the usual test used to assess vitamin D status, but routine screening of every healthy adult is not universally recommended. If you have clinical risk factors, symptoms of vitamin D deficiency, osteoporosis, malabsorption, kidney or liver disease, you may speak to your healthcare professional for a vitamin D test. ^[3][6]

Key takeaway

Remember: Vitamin D deficiency in the elderly is usually not caused by one factor alone. Ageing skin, less time outdoors, low dietary intake, malabsorption, kidney or liver disease, obesity and medicines can all play a role. The safest next step is to review the person’s overall risk, diet, medicines and medical conditions before deciding on testing or supplementation. ^[1–4]

Frequently Asked Questions

Why are elderly people more prone to vitamin D deficiency?

Ageing skin produces less vitamin D after UVB exposure, and older adults are more likely to spend time indoors or have a lower dietary intake. Malabsorption, kidney disease, obesity and some medicines can add to the risk. ^[2][3]

What are the symptoms of vitamin D deficiency in older adults?

Some people have no obvious symptoms. When symptoms occur, they can include bone and joint pain or muscle weakness, but these are not specific to vitamin D deficiency. A healthcare professional may recommend a blood test when symptoms and risk factors make deficiency more likely. ^[1][3]

How much vitamin D does an elderly person need each day?

The Malaysian RNI (recommended nutritional intake) for adults over 65 is 800 IU of vitamin D per day. However, people with diagnosed deficiency, osteoporosis, malabsorption or kidney disease may need a different plan under medical supervision. ^[5]

Is vitamin D3 better than vitamin D2 for older adults?

Both forms can raise vitamin D levels. The Malaysian osteoporosis guideline notes that with daily dosing, vitamin D2 and D3 appear similarly potent, while D3 may be more potent with intermittent dosing. Vitamin D2 and vitamin D3 are derived from different sources: vitamin D2 is derived from plant sources, whereas vitamin D3 is from animal sources. The choice depends on the clinical dosing plan as well as the individual’s dietary preference. ^[5]

Can vitamin D deficiency be treated with sunlight alone?

Not reliably. Sunlight contributes to vitamin D production, but the amount produced varies with age, skin tone, clothing, time of day and other factors. Diet and supplements, when appropriate, can provide more predictable intake. ^[3]

Can I take 1,000 IU of vitamin D every day?

Current vitamin D RNI for Malaysian adults is up to 800 IU. Although the U.S. adult tolerable upper intake level for adults is 1,000–4,000 IU/day for vitamin D, an upper limit is a safety ceiling, not a target dose. Older adults with kidney disease, high calcium levels or certain medicines should get personalised advice before supplementing. ^[3][5]

Talk to a CARiNG Pharmacist

Visit your nearest CARiNG Pharmacy to learn more about vitamin D, supplement labels and whether you may need further advice. 

Find your nearest CARiNG Pharmacy

Medical Disclaimer

Medical disclaimer: This article is for general health education and does not replace medical advice, diagnosis or treatment. Vitamin D testing and supplementation should be individualised, especially for people with kidney or liver disease, malabsorption, high calcium levels, osteoporosis, or multiple medicines. Seek advice from a qualified healthcare professional for concerns about symptoms, test results or supplement doses.

References

1. Cleveland Clinic. Vitamin D Deficiency: Causes, Symptoms & Treatment [Internet]. Cleveland (OH): Cleveland Clinic; accessed 11 Aug 2026. Available from: Source
2. National Institutes of Health (US). Sun Protection in the Elderly. In: Sun Protection and Skin Cancer Prevention [Internet]. Bethesda (MD): National Library of Medicine (US); 2020. Accessed 11 Aug 2026. Available from: Source
3. Office of Dietary Supplements, National Institutes of Health (US). Vitamin D – Health Professional Fact Sheet [Internet]. Bethesda (MD): NIH; updated 2025. Accessed 11 Aug 2026. Available from: Source
4. Merck & Co., Inc. Vitamin D Deficiency. MSD Manual Consumer Version [Internet]. Updated 2023. Accessed 11 Aug 2026. Available from: Source
5. Ministry of Health Malaysia, Malaysian Osteoporosis Society, Academy of Medicine Malaysia. Clinical Practice Guidelines: Management of Osteoporosis. 3rd ed. 2022. Source
6. Endocrine Society. Vitamin D for the Prevention of Disease: Clinical Practice Guideline. Published 2024. Accessed 11 Aug 2026. Available from: Source