Vitamin D testing and supplementation

Routine vitamin D testing is NOT recommended for the general population, including healthy adults, pregnant adults, children, and healthy infants. Testing serum 25-hydroxyvitamin D [25(OH)D] should be targeted to patients at higher risk of deficiency or with clinical indications.

When vitamin D testing is appropriate / MBS-funded

Vitamin D testing is appropriate, and funded under MBS criteria, when the patient has one or more of the following:

• Symptoms of, or established, osteoporosis or osteomalacia
• Raised alkaline phosphatase with otherwise normal liver function tests
• Hyperparathyroidism
• Hypocalcaemia, hypercalcaemia, or hypophosphataemia
• Malabsorption, for example:
  • untreated coeliac disease
  • cystic fibrosis
  • short bowel syndrome
  • bariatric surgery
• Deeply pigmented skin
• Chronic lack of sun exposure due to cultural, medical, occupational, or residential reasons
• Medications that reduce vitamin D levels or absorption, for example anticonvulsants
• Chronic renal failure or renal transplant
• Child under 16 with signs or symptoms of rickets
• Infant whose mother has established vitamin D deficiency
• Exclusively breastfed baby with other risk factors
• Sibling under 16 years with vitamin D deficiency

What not to do

Do not routinely measure vitamin D in the general population.

Do not retest vitamin D within 3 months of starting replacement.

Do not routinely use high-dose vitamin D replacement.

Retesting

Once vitamin D levels have normalised, avoid repeated annual testing unless there is a clear clinical reason, especially if the patient’s risk factors or supplementation status have not changed.

If retesting after replacement, wait at least 3 months, and preferably use the same laboratory because results can vary between labs.

Why routine testing is discouraged

Routine testing can lead to:

• Overdiagnosis of uncertain “deficiency”
• Increased healthcare costs
• Unnecessary supplementation
• Patient anxiety
• Testing that does not change management

Vitamin D deficiency does not have a universally agreed diagnostic threshold, and the definition of “low” 25(OH)D remains controversial.

Different organisations use different cut-offs because vitamin D levels vary with:

• season
• sun exposure
• skin pigmentation
• age
• obesity/body mass
• pregnancy
• kidney disease
• malabsorption
• medications, e.g. anticonvulsants
• assay/laboratory variation

Also, the link between mildly low vitamin D levels and non-bone symptoms, such as fatigue, pain, mood, cancer prevention, cardiovascular disease, or general wellbeing, is not strong enough to justify routine screening in low-risk people.

In Australian practice, a common practical target is:

• ≥50 nmol/L: generally considered adequate for bone health
• 30–49 nmol/L: mild deficiency/insufficiency range
• <30 nmol/L: more clearly deficient
• <12.5 nmol/L: severe deficiency, higher concern for osteomalacia/rickets risk

The key point is: don’t treat the number alone.

• A level of 42 nmol/L in an otherwise healthy person may not mean much clinically.
• A level of 42 nmol/L in a patient with osteoporosis, fragility fracture, malabsorption, renal disease, anticonvulsant use, or minimal sun exposure is more clinically relevant.

Supplementation

For adults with mild uncomplicated vitamin D deficiency, suggested replacement is:

• Cholecalciferol 25–50 micrograms daily
• Equivalent to 1000–2000 IU orally daily

A practical target is approximately 10–20 nmol/L above 50 nmol/L, although dose requirements vary depending on absorption, body mass, age, metabolism, and medications.

High-dose vitamin D may be considered only short term in selected cases, such as severe deficiency or higher body mass, and may require specialist advice.

Harms and cautions

Unnecessary supplements add cost without clear benefit.

Vitamin D toxicity is rare but can cause hypercalcaemia.

Vitamin D supplementation is contraindicated or requires caution in conditions where vitamin D metabolism may be abnormal, including:

• Sarcoidosis
• Tuberculosis or other granulomatous disease
• Metastatic bone disease

How to respond when a patient requests vitamin D testing

A useful approach:

1. Explore the patient’s reason for requesting the test.
2. Ask about symptoms suggesting deficiency, bone pain, fractures, falls, weakness, or risk factors.
3. Explain that Medicare funds testing only when specific risk factors or clinical indications are present.
4. Provide bone health advice:
   • weight-bearing exercise
   • adequate calcium and vitamin D intake
   • safe sun exposure
   • falls prevention
   • smoking cessation
   • reducing alcohol intake
5. Consider osteoporosis risk assessment and BMD testing if clinically indicated.

Practical summary

Vitamin D testing should be targeted, not routine. In most low-risk patients, testing does not improve outcomes and may lead to unnecessary treatment. Test when there are clear clinical indications or MBS-eligible risk factors. Treat confirmed mild deficiency with standard-dose cholecalciferol, avoid early retesting, and focus on broader bone health and falls prevention.