GPs are being encouraged not to test routinely for vitamin D deficiency after a new study found that testing had increased unnecessarily.

Our research has shown that the odds of a child having a vitamin D test ordered by a GP has increased 30-fold over 15 years, but this has not increased the detection rates of low vitamin D. 

We call for the development of national strategies to prevent vitamin D deficiency and nutritional rickets in Australia, to align with the 2016 Global consensus recommendations on prevention and management of nutritional rickets.

The signs of vitamin D deficiency

Given the important role that 25-hydroxy vitamin D (vitamin D) plays in maintaining bone health, it is encouraging that GPs are mindful of preventing vitamin D deficiency and nutritional rickets, which can affect the health, growth and development of infants, children and adolescents (here).

Complications of vitamin D deficiency are rare but can be serious.

When accompanied by dietary calcium deficiency, vitamin D deficiency can lead to rickets, limb pain, fractures, and even hypocalcaemic seizures (here and here).

In Australia, the incidence of vitamin D deficiency is 4.9 cases per 100 000 children aged less than 16 years, and high risk groups include infants who are exclusively breastfed for more than six months, refugees, children with dark skin colour, and those who are extensively covered by clothing due to cultural reasons (here).

Population level data on the relationship between vitamin D deficiency and socio-economic status are not currently available in Australia.

GPs urged not to routinely test children for vitamin D - Featured Image
The odds of a child having a vitamin D test ordered by a GP has increased 30-fold over 15 years. Jarun Ontakrai/Shutterstock

What we studied

Our study of vitamin D testing in children aged less than 18 years attending general practice in three Primary Health Networks in Victoria, showed that the odds of a child having a serum 25-hydroxyvitamin D (25OHD) test increased 30-fold from 2003 (45 tests) to 2018 (8378 tests).

This represents an estimated total cost increase from $1352 to $251 759 based on the current Medicare Benefits Schedule (MBS) item 66833 cost of $A30.05.

However, the odds of detecting a low vitamin D level (25OHD < 50nmol/L) stayed steady over the 15 years, with the odds ratio (OR) falling to less than 1.0 from 2015 onwards compared with 2003.  

This means that despite increased testing, the chance of detecting a low result in the tested paediatric population was lower in 2018 (OR, 0.61; 95% confidence interval [CI], 0.21–0.32) than in 2003.

Repeated testing when the initial test is normal represents potentially wasted resources in terms of time and money.

Vitamin D testing was repeated in 19.2% of patients (4702 tests at an estimated cost of $141 295) when the initial test was normal.

The median interval between testing and retesting was 357 days, suggesting annual retesting may simply be routine practice for some GPs.

The low prevalence of vitamin D deficiency would suggest, however, that even if population screening were indicated, GPs are not screening the appropriate children (Box 1).

Worryingly, when vitamin D deficiency was detected (25OHD < 30nmol/L) on the initial test (4603 test results), a follow-up test within three months, as recommended by the global consensus recommendations, was done in only in 180 (3.9%). Routine testing of vitamin D provides limited clinical value for prevention of rickets and other complications. The utility is further reduced unless children are also treated and followed up when deficiency is detected.

The dataset did not include information about the children’s diagnoses and treatment, nor any information on the reasons for requesting vitamin D tests by GPs when deciding to test or retest. This requires further research using a mixed methods approach to better understand the decision-making processes regarding vitamin D testing in children and adolescents.

Global consensus recommendations

The global consensus recommendations do not recommend routine screening for vitamin D in children unless there are signs and/or symptoms, but they do recommend vitamin D supplementation (Box 1).

Taking a population health approach suggests that supplementation is an effective and equitable strategy for the prevention of nutritional rickets. Supplementation is cheap, approximately AU$24 per year compared with the cost of one pathology test; for example, MBS item 66833 incurs a cost of $A30.05 per test (here).

For this reason, many countries, including Canada and the United Kingdom, have implemented mandatory fortification of common foods to prevent nutritional rickets (here), but this is not the case in Australia.

As noted, the reported incidence rate of nutritional rickets in Australia is 4.9 cases per 100 000 children aged less than 16 years — higher than in Canada (2.9 cases per 100 000). Given the demonstrated benefits of food fortification in the UK, Canada and several European countries, fortification of staple foods with vitamin D and calcium should be considered to prevent vitamin D deficiency and rickets in Australian children.

Box 1. Take-home message for vitamin D testing and supplementation in children according to the global consensus recommendations (here)
Do not routinely test for vitamin D in children or adolescents
Do prescribe a vitamin D supplement (cholecalciferol) for:
– All infants from birth to 12 months — 400 IU per day
– All pregnant women — 600 IU per day
– All at-risk groups* over 12 months of age — 600 IU per day
Fortification of staple foods with vitamin D and calcium as appropriate
*Children at risk of vitamin D deficiency, including those who have dark skin colour, extensive skin covering (eg, for cultural reasons, extensive application of sun protection), restricted exposure to sunlight, prolonged exclusive breast feeding (more than six months), seasonal variation at high latitudes, restricted dietary intake and, gut malabsorption syndromes or chronic liver disease.

Testing for an isolated vitamin D level also holds limited clinical utility. Alkaline phosphatase (ALP) levels should be measured at the same time because a high ALP level may be a more accurate indicator of osteomalacia or rickets (here). However, in our study just over a half of vitamin D tests (N = 35 488; 57.8%) were accompanied by an ALP test — and in only 0.7% of these, the results were consistent with nutritional rickets (elevated ALP and low vitamin D) (here).

The global consensus recommendations are at odds with the current Royal Australian College of General Practitioners’ (RACGP) statement on vitamin D testing published in November 2022 and the MBS schedule, which states that vitamin D testing is appropriate if the patient:

  • is an infant whose mother has established vitamin D deficiency; or
  • is an exclusively breastfed baby and has at least one other risk factor; or
  • has a sibling who is less than 16 years of age and has vitamin D deficiency.

In all of these scenarios, the global consensus recommendations state that testing is not required but vitamin D supplementation most certainly is (Box 1). The reasons for this misalignment with the global consensus recommendations are unclear but may be related to the lack of dissemination and implementation of the global consensus recommendations. Clearly, publishing recommendations in a peer-reviewed journal is not enough to influence practice and an implementation strategy is needed (here).

In addition, the RACGP statement and the MBS guidance only cover vitamin D testing, they do not specifically address prevention and treatment of vitamin D deficiency or nutritional rickets.

Testing for vitamin D has little impact on preventing nutritional rickets. We also know that GPs want to ensure the best health for children who may be at risk of low vitamin D levels, or vitamin D deficiency and rickets. In these situations, supplementation with vitamin D and not evaluation of vitamin D levels is warranted as it will provide appropriate management without the need for a blood test. However, if testing for vitamin D is undertaken, doing so is only worthwhile if test results are reviewed and children who were deficient are treated and retested. The data from our study suggest the opposite; retesting occurred more frequently when the initial test was normal while retesting seldom occurred when the initial test detected vitamin D deficiency.

The global consensus recommendations recognise that clinicians are busy and health systems are underfunded, and they therefore recommend vitamin D supplementation rather than testing as a more equitable as well as time- and cost-effective approach to treat vitamin D deficiency and rickets.

Other impacts include significant environmental costs associated with testing and retesting including adding to plastic waste and the carbon footprint of health care (here). There are also costs in terms of disruptions for families who need to take their child to have a blood sample taken. Furthermore, drawing blood from a young child can be traumatic not only for the child but for their parents or carers and the pathology collector.

The need for national strategies

To improve care for children and families and support GPs in the prevention of vitamin D deficiency and nutritional rickets in Australia, we need to develop national strategies for the implementation of the Global consensus recommendations on prevention and management of nutritional rickets.

Aligning current Australian recommendations and MBS reimbursement rules may be a good first step to increase high value practice to prevent nutritional rickets and to reduce low value testing.

Professor Yvonne Zurynski is the Professor of Health System Sustainability at the Australian Institute of Health Innovation at Macquarie University.

Professor Craig Munns is the Director of the Child Health Research Centre at the University of Queensland, a paediatrician at Queensland Children’s Hospital, and Honorary Professor at Macquarie University.

Professor Andrew Georgiou is a health informatics researcher at the Australian Institute of Health Innovation at Macquarie University.

Professor Munns is the spokesperson for this study.

The statements or opinions expressed in this article reflect the views of the authors and do not necessarily represent the official policy of the AMA, the MJA or InSight+ unless so stated. 

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7 thoughts on “GPs urged to avoid overtesting for vitamin D

  1. Anonymous says:

    No mention of deficiencies in adults. My hit rate for Vitamin D deficiency in adults is high. Vitamin D is important not only for bone health. Vitamin D is a neurosteroid important for brain health.

  2. Anonymous says:

    1. A clear selection bias exists in this study, yet its recognition remains absent. The vast majority of children attending general practice would not undergo pathology testing. Among the minor subset that did so in this study—amounting to nearly one million cases across a span of over a decade—only 6.4% underwent vitamin D testing. If you consider the spectrum of children accessing general practice, this proportion is likely to be exceedingly small. Selecting a patient for testing or referring them to a clinician in secondary care tends to trigger a chain of additional tests (a diagnostic cascade), so by default, only examining those children tested inflates the finding. Similarly, it would be reasonable to anticipate a further rise in the proportion of children subjected to vitamin D testing by paediatricians given the inherent nature of specialised care.

    2. Its important not to confuse temporal trends with unwarranted variations in care. Without acknowledging the clinical context (reasons for patient encounters were not investigated), making comparisons to a definitive standard is not feasible. Nonetheless, an attempt to assess changes in practice across comparable groups remains unmade.

    3. The choice to scrutinise a solitary test implies that the observed escalation in vitamin D testing over time is a phenomenon unique to vitamin D testing or to general practice. In reality, the rise in testing is a pervasive trend across various tests and specialities and is by no means exclusive to general practice (start here:

    4. I’m intrigued by the potential benefits of engaging GPs with an understanding of the clinical context behind primary care EMR data. Additionally, I contemplate how paediatricians might react if GPs were to evaluate and offer critiques on practices within secondary care, such as suggesting “paediatricians should do more or less of x”. While I anticipate that the response might not be positive, it does shed light on the deeply ingrained culture within the medical sphere.

  3. Silva says:

    having Low level of deficiency detected in the study- Global recommendation is still advised ? Supplements to all new born. all pregnant women;
    Is it ethical to prescribe non water soluble vitamin without a baseline assessment in a developed country like Australia.

  4. Dr Cedric Meyerowitz says:

    If so rare, why does all paediatricians do a Vitamin-D test on all patients they see, and a lot of them repeat it every few months, even if normal

  5. Andrew Nielsen says:

    So what proportion of the tests were positive?

  6. Andrew W says:

    For patients to maintain compliance its helpful to demonstrate degree of deficiency. The initial replacement dose to correct levels varies and needs a level to determine. A follow-up level can allow dose reduction to a maintenance dose. 30 nmol/L is a low bar for deficiency based on bone metabolism. Reasonable epidemiological evidence suggests > 75nmol/L is associated with best health outcomes. There is a difference between health maintenance and serious illness prevention. No point having single guideline for a country that spans such a broad range of latitudes with such a broad range of cultural practices – judgement needed.

  7. Anonymous says:

    No mention of deficiencies in the elderly!

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