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Vitamins & Minerals

Vitamin D (25-OH)

Vitamin D is checked with a blood test to see whether your body has enough for healthy bones. In Australia, an adequate level is generally 50 nmol/L or above, year-round. Your level naturally shifts with the seasons — the same person can test quite differently in summer versus winter — so the number only tells part of the story on its own.

Standard Care
CategoryVitamins & Minerals
Reference rangeSee your report
Evidence✓Standard Care
Last updated3 July 2026
On this page
Over 30%

of Australian adults have a mild, moderate or severe vitamin D deficiency.

What is vitamin d (25-oh)?

Vitamin D is a fat-soluble nutrient that helps your body absorb calcium and maintain healthy bones. Most of your vitamin D comes from sunlight on your skin, with smaller amounts from foods such as oily fish, egg yolks and fortified products. The blood test measures 25-hydroxyvitamin D (25-OH D) — the storage form that circulates in your blood and reflects how well stocked your body is. It is the standard way to check your vitamin D status.

Why is it tested?

The 25-OH D test is used to check that your body has an adequate supply of vitamin D. Your GP may order it if you have risk factors for low vitamin D. Those include spending most of your time indoors, having naturally darker skin, regularly covering your skin, having a condition that affects how you absorb nutrients, being older, or being pregnant or breastfeeding. It is also a routine part of looking into bone health.

Reference range (Australia)

Adequate: 50 nmol/L or above (year-round) nmol/L

Australian thresholds for 25-OH D: sufficient/adequate ≥50; mild deficiency 30–49; moderate deficiency 12.5–29; severe deficiency below 12.5 nmol/L. Levels are seasonal — a result may need to be 10–20 nmol/L higher at the end of summer to stay adequate through winter. Laboratory reference intervals can vary, so also use the range on your own report.

Reference intervals vary between laboratories. Always use the range printed on your own report.

What your result means

If your level is low

A result below 50 nmol/L is generally considered low for bone health in Australia. Deficiency is graded in bands: mild (30–49 nmol/L), moderate (12.5–29 nmol/L) and severe (below 12.5 nmol/L). Low levels commonly relate to limited sun exposure or the season. They can also reflect naturally darker skin, regularly covering the skin, or conditions that affect how well your gut absorbs nutrients. Your GP can put your specific result in context.

If your level is in range

A result of 50 nmol/L or above is generally considered adequate for bone health year-round — good news. Because levels are highest in late summer and lowest at the end of winter, your GP will often take the season into account too. A result that looks comfortable in February may sit closer to the boundary by August, and that is normal.

If your level is high

A result well above the usual range is uncommon and is most often related to vitamin D supplementation. Sustained very high vitamin D and calcium can lead to calcification — where calcium deposits build up in soft tissue — and can affect organs such as the kidneys. If you take high-dose supplements, it is worth mentioning this to your GP so they can keep an eye on the level.

What can affect your result

In Australia the main source of vitamin D is sunlight on the skin, so your level follows the seasons. It tends to peak in late summer and drop to its lowest at the end of winter. Where you live, your skin type and how much skin is exposed all affect how much your body makes from sun. Naturally darker skin, regularly covering the skin, and spending most of your time indoors each reduce the amount produced. Conditions that affect absorption or processing — such as coeliac disease, inflammatory bowel disease, and chronic kidney or liver disease — can also lower vitamin D. Some medicines have the same effect, particularly certain anti-epilepsy treatments. Food is a minor source and contributes only small amounts.

When to act

If your result is below 50 nmol/L, or if you have risk factors for low vitamin D, it is worth raising at your next visit. Your GP can put the number in context alongside the season, your sun exposure and any symptoms you have noticed. Recovery can be slow — levels often take several months to climb — so a follow-up test down the track can show how things are moving. Because vitamin D and calcium work closely together, your GP may also look at related results such as calcium and PTH (parathyroid hormone, which the body uses to regulate calcium levels). This page is general information and is not a substitute for advice from your GP.

Frequently asked questions

Australian guidance generally considers 50 nmol/L or above adequate for bone health, year-round. The RCPA (Royal College of Pathologists of Australasia) describes levels under 30 nmol/L as deficient, 30–50 nmol/L as mildly deficient, and above 50 nmol/L as sufficient for bone health. Keep in mind that laboratory reference intervals can vary slightly, so it is always worth reading the range printed on your own report alongside this guidance.

Vitamin D levels are highest in late summer and lowest at the end of winter, so the same person can test quite differently across the year. Because your body needs a buffer to carry it through the cooler months, a result may need to be 10–20 nmol/L higher at the end of summer to stay adequate through winter. Your GP takes the season into account when reading your number, which is one reason the result is not always as straightforward as a pass or fail.

In Australia most vitamin D comes from sunlight rather than food, and how much your skin makes depends on the season, your location, your skin type and how much skin is exposed. Despite plentiful sun in much of the country, over 30% of Australian adults have a mild, moderate or severe vitamin D deficiency — often because modern life keeps people indoors during peak UV hours or because they cover up to protect against skin cancer.

A level below 50 nmol/L is generally considered low for bone health. There are three bands of deficiency (all in nmol/L): mild (30–49), moderate (12.5–29) and severe (below 12.5). What the number actually means for you depends on the season, your risk factors and any symptoms. Your GP can put all of that together and is the right person to work through what, if anything, to do about it.

Very high levels are uncommon and usually relate to supplementation rather than sun exposure alone. Sustained high vitamin D and calcium can lead to calcification — where calcium deposits build up in places they should not — and can put strain on the kidneys and other organs. If you take high-dose supplements, it is worth letting your GP know so they can keep an eye on the level over time.

Test your vitamin d (25-oh)

NATA-accredited testing. Results in 2–5 days. No GP referral required.

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