Year 2019
July 2019
09 July 2019

Notes on Vitamin D Insufficiency


Ms T, a 56 year old lady attended a recent health screening and had a thorough check, and no abnormalities were detected except for a low level of 25OH Vitamin D of 23.7 ng/mL. She had no past medical history of note and there was a family history of Type 2 Diabetes which her father had. She is asymptomatic, with no bone pain or muscle aches and she had her menopause at age 52. She is concerned and has questions:

  1. What does this low value mean?
  2. Do I need any other tests?
  3. Do I need treatment?
  4. Are there any side effects?

Definitions and clinical presentation of vitamin deficiency/ insufficiency

Various organizations, institutes, societies and foundations define deficiency as a serum 25[OH]D of less than 10 ng/mL and sufficiency between 20 to 30 ng/mL. In Singapore, normal laboratory reference values are defined as greater than 30 ng/mL.

Clinical manifestation of this condition is largely dependent on the severity and duration of the deficiency or insufficiency. Overt vitamin D deficiency, often presents with bone pain and tenderness, muscle weakness, difficulty walking and a waddling gait. It is characterized by hypocalcaemia and hypophosphataemia, and results in osteomalacia in adults and rickets in children. These conditions are uncommon in developed countries. The majority of patients with moderate to mild vitamin D insufficiency (serum 25[OH]D between 15 and 20 ng/mL, respectively) are asymptomatic. However, with prolonged deficiency, there is reduced intestinal absorption of calcium and phosphorus and hypocalcaemia may ensue, causing hyperparathyroidism, which leads to phosphaturia, bone demineralization and when prolonged, osteomalacia in adults.

The causes for vitamin D insufficiency are listed in table 1, and in addition, are also more prevalent in certain groups of individuals such as the elderly, those confined to the indoors, those living in the northern latitudes, those who are dark skinned, obese, hospitalized or institutionalized or with concomittant osteoporosis.

Table 1. Causes of vitamin D insufficiency

The majority of individuals with asymptomatic vitamin D insufficiency do not require any additional investigations. Patients with serum 25(OH)D levels of <10 should have further evaluation to measure serum calcium, phosphorus, alkaline phosphatase, parathyroid hormone and renal function. Radiological imaging may be indicated for individuals with bone pain.

Vitamin D supplementation

The goal of Vitamin D supplementation is for skeletal benefits such as improvement of bone density, improvement of muscle strength and prevention of falls. Extra-skeletal benefits to the immune and cardiovascular system have not been demonstrated convincingly in clinical trials.

Higher food intake of vitamin D containing foods or increased sun-exposure are generally inadequate or have other side effects such as excessive ultra-violet light exposure to the skin. For individuals with vitamin D deficiency serum 25(OH)D levels <10 ng/mL, a loading dose of 50,000 IU of vitamin D2 or vitamin D3 orally once per week for 6 to 8 weeks is recommended followed by a maintenance daily dose of 800 to 1000 IU of vitamin D3. Monthly preparations are also available. Moderate and mild vitamin D insufficiency (serum 25(OH)D levels of 10 to 20 and 20 to 30 ng/mL, respectively) require daily supplementation of 800 to 1000 IU and 600 to 800 IU, respectively. For children aged 1 to 18 years old, a daily maintenance dose of 600 to 1000 IU is recommended.

Individuals should be reviewed for symptoms and serum 25(OH)D levels checked to ensure adequate supplementation.

Adverse side effects of over-replacement are rare and include hypercalciuria and hypercalcaemia which are usually observed at serum 25(OH)D levels above 150 ng/mL. Symptoms of hypercalcaemia such as confusion, polyuria, polydipsia, anorexia, vomiting and muscle weakness may occur. In these instances, individuals should discontinue the vitamin D supplementation and reduce calcium intake.

Individuals with vitamin D insufficiency in certain population groups or clinical conditions, such as in pregnancy, concomitant malabsorptive disorders, chronic kidney disease, co-existing hyperparathyroidism or osteoporosis, may require adjustments to their therapy (table 2).

Table 2. Special populations of individuals with vitamin D insufficiency and considerations to note during vitamin D supplementation.


Vitamin D insufficiency is common and associated with many other conditions. A large proportion of individuals are asymptomatic and do not require further evaluation. Individuals with very low levels of vitamin D or symptomatic may require further investigations to exclude osteomalacia or rickets (in adults or children, respectively). Vitamin D supplementation can be done safely with little risk of side effects. Interval reviews and monitoring are recommended.

To answer Ms T’s queries:

  1. What does this low value mean?

She has insufficient vitamin D levels and is asymptomatic. She is post-menopausal and may be at risk of developing osteoporosis.

  1. Do I need any other tests?

She does not need any further evaluation for vitamin D insufficiency. If there are other symptoms such as bone pain or muscle weakness, she would require further tests.

  1. Do I need treatment?

Yes, she should be advised to take 800-1000 IU of vitamin D3 supplementation per day.

  1. Are there any side effects?

There is a small risk of over-replacement which may cause hypercalcaemia or hypercalciuria. However, this can be reduced through cautious and appropriate dosing and interval reviews.


Dawson-Hughes B, Mithal A, Bonjour JP, et al. IOF position statement: vitamin D recommendations for older adults. Osteoporos Int 2010; 21:1151-4.

Michael F. Holick Neil C. Binkley Heike A. Bischoff-Ferrari Catherine M. Gordon David A. Hanley Robert P. Heaney M. Hassan Murad Connie M. Weaver Evaluation, Treatment, and Prevention of Vitamin D Deficiency: an Endocrine Society Clinical Practice Guideline The Journal of Clinical Endocrinology & Metabolism, Volume 96, Issue 7, 1 July 2011, Pages 1911-30

Institute of Medicine. 2011. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: The National Academies Press

American Geriatrics Society Workgroup on Vitamin D Supplementation for Older Adults. Recommendations abstracted from the American Geriatrics Society Consensus Statement on vitamin D for Prevention of Falls and Their Consequences. J Am Geriatr Soc 2014; 62:147-52.

A Specialist’s Point of View – Written by Dr Eric Khoo Yin Hao

MBChB, Leicester, UK
Fellow of Royal College of Physician, UK
Doctor of Medicine, Nottingham, UK

Dr Eric Khoo is an Endocrinologist currently practicing at Gleneagles Medical Centre and is a visiting consultant to NUH. As a member of the Division of Endocrinology, NUH and School of Medicine, NUS from 2009 to 2018, he served as diabetes service director, clinical service director and head of Endocrinology. He manages diabetes, thyroid, pituitary, adrenal and metabolic bone conditions and has an interest in the role of diet, lifestyle and pharmacotherapy in metabolic diseases and diabetes mellitus and the associated comorbidities and complications.

Eric Khoo Diabetes and Endocrine Clinic
6 Napier Road #09-16, Gleneagles Medical Centre Singapore 258499.
Tel: 62591778
Fax: 62591782
Email: [email protected]

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