Do You Need a Vitamin D Blood Test This Winter?

More than 1 in 4 Australian adults were vitamin D deficient in winter in the latest Australian Bureau of Statistics National Health Measures Survey, and in Tasmania that figure was nearly 1 in 2. That’s a surprising statistic for a country famous for sunshine, beaches and outdoor living — but it also explains why so many Australians start wondering about a vitamin D blood test when winter fatigue, muscle aches or “I just feel flat” symptoms creep in.

So, do you need a vitamin D blood test this winter?

Quick answer: maybe — but not everyone does. Vitamin D levels can dip in winter, especially in southern Australia, but routine screening of healthy adults is not generally recommended. A blood test is most useful when you have symptoms, risk factors, relevant medical conditions, or when your doctor wants to confirm deficiency before treatment. The key is knowing when a blood test referral is sensible, what the result actually means, and what to ask your doctor before you spend time and money on testing.

In this guide, we’ll walk through what vitamin D does, why winter changes your risk, who is more likely to need testing, how a vitamin D blood test works in Australia, and how to approach supplements safely. We’ll also explain how we can help at NextClinic if you need a doctor-led pathology referral online, where clinically appropriate.

This article is general health information for Australian residents and is not a substitute for personalised medical advice. If you feel seriously unwell, have chest pain, severe shortness of breath, fainting, confusion, sudden weakness, or thoughts of self-harm, seek urgent medical care or call 000.

Why vitamin D matters more than you might think

Vitamin D is often called a vitamin, but it acts more like a hormone in the body. It helps your body absorb and use calcium and phosphorus, which are essential for healthy bones, teeth and muscles. Healthdirect explains that the vitamin D blood test measures 25-hydroxy-vitamin D, the form used to assess how much vitamin D is available in your body.

Your body gets vitamin D in two main ways:

• Sun exposure: your skin makes vitamin D3 when exposed to UVB radiation.
• Diet and supplements: small amounts come from foods such as fatty fish, eggs, UV-exposed mushrooms, red meat and fortified foods, and from vitamin D supplements.

The tricky part in Australia is balance. The same ultraviolet radiation that helps your body make vitamin D is also the major cause of skin cancer. Cancer Council Australia puts it clearly: in Australia, we need to balance skin cancer prevention with maintaining adequate vitamin D levels.

That balance can feel confusing. On one hand, you hear “protect your skin”. On the other, you hear “get enough vitamin D”. In winter, especially if you live in Melbourne, Hobart, Canberra, Adelaide, Perth or regional southern Australia, it’s easy to spend most of your daylight hours indoors, rugged up, commuting in the dark and seeing very little midday sun.

That’s where the winter vitamin D conversation begins.

Vitamin D deficiency Australia: why winter changes the odds

Vitamin D deficiency in Australia is not just a “cold country” problem. The ABS found that 20.6% of Australian adults had vitamin D deficiency in 2022–24. The rate was higher in winter, with 26.1% of adults deficient in winter compared with 15.5% in summer.

The seasonal pattern makes sense. In winter:

• the sun sits lower in the sky
• UVB radiation is weaker in many southern areas
• people cover more skin with clothing
• daylight hours are shorter
• outdoor activity often drops
• many people commute before sunrise and return after dark

The winter effect is not equal across the country. The ABS reported winter vitamin D deficiency rates of 45.7% in Tasmania, 42.9% in the ACT, 33.3% in Western Australia, 32.2% in Victoria, and 28.6% in South Australia, compared with 15.8% in Queensland.

That does not mean everyone in southern Australia needs a test every winter. It does mean winter is a good time to pause and ask: “Do I have risk factors that make low vitamin D more likely?”

Can low vitamin D cause winter fatigue?

This is the question many people are really asking.

You might not be thinking, “I wonder what my 25-hydroxyvitamin D level is?” You might be thinking:

• “Why am I exhausted all the time?”
• “Why do my legs feel weak?”
• “Why am I waking up tired?”
• “Is this just winter fatigue, or something else?”
• “Should I ask for a vitamin D blood test?”

Low vitamin D can be associated with bone pain, muscle weakness and musculoskeletal symptoms, especially when deficiency is moderate to severe. Australian Prescriber notes that moderate to severe vitamin D deficiency is causally associated with osteomalacia in adults and rickets in children, while deficiency is also important in osteoporosis and fracture risk.

But there’s an important “but”: fatigue has many possible causes.

Winter fatigue can be linked to poor sleep, viral illness, stress, burnout, low iron, thyroid disease, depression, anxiety, sleep apnoea, medication effects, chronic inflammation, pregnancy, alcohol use, shift work, long COVID, or simply trying to do too much with too little recovery. Vitamin D may be one piece of the puzzle, but it is rarely the whole puzzle.

That’s why a good doctor won’t usually treat “tiredness” as a single-test problem. They’ll ask about the pattern of your fatigue, sleep, mood, diet, menstrual history, medications, infections, weight changes, pain, exercise tolerance and red-flag symptoms. If your tiredness has been lingering, you might also find our guide Worried About Lingering Fatigue? Read This helpful.

What is a vitamin D blood test?

A vitamin D blood test checks your blood level of 25-hydroxy-vitamin D, often written as 25(OH)D. This is considered the best marker of vitamin D status because it reflects vitamin D from both skin production and dietary or supplemental sources. The Royal College of Pathologists of Australasia recommends measuring vitamin D as 25-hydroxyvitamin D and reporting it in nmol/L in Australia and New Zealand.

In practical terms, the process is simple:

1. You speak with a doctor.
2. If clinically appropriate, the doctor gives you a pathology request form or blood test referral.
3. You take the referral to a pathology collection centre.
4. A blood sample is taken from a vein in your arm.
5. The result is sent back to the requesting doctor.
6. Your doctor interprets the result in the context of your symptoms, risk factors and medical history.

Healthdirect notes that you usually need a referral to get a vitamin D blood test in Australia, and no special preparation is usually required for the vitamin D test itself. If other blood tests are ordered at the same time, you may need separate instructions, such as fasting for certain tests.

Do you actually need a vitamin D blood test referral?

Not always.

The RCPA position statement says that measuring 25(OH)D is appropriate as a case-finding strategy in people at risk of vitamin D deficiency, but routine screening of healthy adults, healthy infants, healthy children and pregnant women is not currently recommended.

That means a vitamin D blood test is not like a universal “winter check-up” that every Australian automatically needs. It is more targeted.

A doctor may consider a blood test referral if you have symptoms or risk factors such as:

• bone pain or suspected osteomalacia
• muscle weakness or unexplained musculoskeletal pain
• osteoporosis, osteopenia, low-trauma fractures or planned osteoporosis treatment
• abnormal calcium, phosphate, alkaline phosphatase or parathyroid hormone results
• malabsorption conditions such as inflammatory bowel disease, untreated coeliac disease, cystic fibrosis, short bowel syndrome or previous bariatric surgery
• chronic kidney disease or kidney transplant history
• certain medications that can reduce vitamin D levels, particularly some anticonvulsants
• naturally dark skin, because higher skin pigment reduces UV penetration
• chronic lack of sun exposure due to indoor work, shift work, disability, illness, institutional care, cultural clothing, religious clothing or intentional sun avoidance
• obesity
• a history of skin cancer or high skin cancer risk that leads you to avoid sun exposure
• pregnancy or breastfeeding with additional risk factors
• an infant whose mother has established vitamin D deficiency
• a child with signs or risk factors for rickets

Cancer Council Australia also lists several groups at increased risk of deficiency, including naturally dark-skinned people, people who cover their skin for cultural or religious reasons, frail or elderly people who live mostly indoors, people with obesity, infants of vitamin D deficient mothers, people with absorption issues or certain medications, and people avoiding sun because of previous skin cancer or high skin cancer risk.

If you fit one or more of these groups, asking your doctor about a vitamin D blood test is reasonable.

When you might not need testing

You may not need a vitamin D blood test if you are generally well, have no risk factors, get regular safe outdoor exposure, have no bone or muscle symptoms, and are not being assessed for a condition where vitamin D status matters.

This can surprise people. Many Australians assume more testing is always better. But medical testing works best when the result is likely to change what happens next. If the chance of deficiency is low, a test may not add much value. It may also lead to unnecessary repeat tests, anxiety about borderline results, or supplements you may not need.

There are situations where your doctor may recommend practical lifestyle steps rather than testing straight away. For example, if you are low risk and simply spending less time outdoors in winter, your doctor might suggest safe sun exposure, diet changes, or a standard over-the-counter supplement if appropriate. On the other hand, if you have risk factors or symptoms, testing may help guide the right dose and follow-up plan.

How to understand vitamin D blood test results in Australia

Vitamin D results in Australia are usually reported in nmol/L.

Many Australian sources use these cut-offs:

• Adequate: 50 nmol/L or above
• Mild deficiency: 30–49 nmol/L
• Moderate deficiency: 13–29 nmol/L
• Severe deficiency: below 13 nmol/L

The ABS uses these categories in its vitamin D biomarker reporting and notes that test results should be interpreted with a health professional rather than used alone to confirm a diagnosis.

A few important points:

First, a result is not just a number. Your doctor will interpret it alongside your symptoms, risk factors, season, medical history, medications and other pathology results.

Second, winter timing matters. A level that looks “okay” at the end of summer may fall by the end of winter. The ABS methodology notes that RCPA advice indicates vitamin D levels may need to be 10–20 nmol/L higher at the end of summer to allow for seasonal decline in winter.

Third, more is not always better. Very high vitamin D levels can be harmful, especially if caused by high-dose supplements. The ABS notes that serum vitamin D levels above 125 nmol/L are linked to potential adverse effects, particularly above 150 nmol/L.

Fourth, if you start treatment, retesting is not usually immediate. RCPA recommends retesting serum 25(OH)D no earlier than three months after starting vitamin D supplementation or changing the dose.

Safe sun exposure: the Australian balancing act

Because sunlight is the main natural source of vitamin D, it’s tempting to think the answer is simply “get more sun”. In Australia, that advice needs care.

Cancer Council Australia recommends sun protection when the UV Index is 3 or above, or when spending extended periods outdoors. In some southern areas of Australia, UV may fall below 3 in late autumn and winter, and sun protection may not be required for short periods unless you are at high altitude, near reflective surfaces like snow, working outdoors, or outside for extended periods.

Cancer Council also advises that when UV is below 3 in late autumn and winter in some southern areas, spending time outdoors in the middle of the day with some skin uncovered can help vitamin D levels, and being physically active outdoors can help too.

The key phrase is safe exposure.

A sensible winter approach might include:

• checking the UV Index through the Bureau of Meteorology or SunSmart app
• going for a short walk around midday when UV is low
• exposing forearms or hands briefly if appropriate for your skin type and health situation
• continuing sun protection whenever UV is 3 or above
• avoiding sunburn completely
• seeking medical advice if you have a history of skin cancer, high skin cancer risk, photosensitivity, or take medicines that increase sun sensitivity

Cancer Council is clear that overexposure to UV is never recommended, even if you have vitamin D deficiency. If you’re concerned about your level, speak with your doctor about whether supplementation is safer than additional sun exposure.

What about vitamin D supplements?

Vitamin D supplements can be helpful when someone has confirmed deficiency or strong risk factors, but they should be used thoughtfully.

For many people, vitamin D3 supplements are available over the counter. However, dose, duration and follow-up depend on your level, your age, your medical conditions, your medications, your pregnancy or breastfeeding status, your calcium intake, and whether you have kidney disease, malabsorption or osteoporosis.

Australian Prescriber notes that many supplements in Australia contain cholecalciferol, or vitamin D3, and that higher doses may be needed in some situations, such as severe deficiency, obesity, certain medications or malabsorption-related conditions. It also highlights that high-dose annual therapy has been associated with increased falls and fractures in one Australian study, which is a reminder not to self-prescribe mega-doses.

In other words: don’t panic-buy the strongest vitamin D product you can find. More is not automatically better.

Ask your doctor or pharmacist:

• Do I actually need a supplement?
• What dose is appropriate for my result and risk factors?
• How long should I take it?
• Should I take it daily, weekly or another way?
• Do I need calcium as well?
• Could it interact with my medications?
• When should I repeat the blood test?
• What symptoms should prompt review sooner?

If you are pregnant, breastfeeding, have kidney disease, high calcium, sarcoidosis, lymphoma, parathyroid disease, kidney stones, or take multiple supplements, get medical advice before taking vitamin D.

What to ask your doctor before requesting a vitamin D blood test

If you’re booking a consultation because of winter fatigue or concern about vitamin D deficiency Australia, it helps to arrive with clear questions.

Try asking:

“Do my symptoms fit vitamin D deficiency, or should we investigate other causes too?” This is especially important if fatigue is your main symptom. Your doctor may also consider iron studies, B12, folate, thyroid function, kidney and liver function, blood count, blood glucose, inflammatory markers, pregnancy testing, sleep assessment or mental health screening.

“Do I have risk factors that make a vitamin D blood test worthwhile?” Mention your work hours, sun exposure, skin tone, clothing coverage, diet, supplement use, medical conditions and medications.

“Which vitamin D test are you ordering?” For vitamin D status, the relevant test is generally serum 25-hydroxyvitamin D, or 25(OH)D.

“What result would change my management?” This helps you understand why the test is being ordered and what the plan will be if it is low, borderline or normal.

“If my vitamin D is normal, what’s next?” A normal vitamin D result does not mean your fatigue is imaginary. It means your doctor should consider other causes.

“When should I retest?” If you start supplements, retesting too early may not be useful. RCPA recommends retesting no earlier than three months after starting or changing supplementation.

When winter fatigue needs medical review

Feeling a bit slower in winter is common. But fatigue that persists, worsens or interferes with daily life deserves attention.

Book a medical review if:

• fatigue lasts more than two weeks without a clear reason
• you feel weak rather than just tired
• you have bone pain, muscle weakness or repeated falls
• you have unexplained weight loss
• you have night sweats or persistent fever
• you feel short of breath with usual activity
• your periods are very heavy
• you are pregnant or recently gave birth
• you have low mood, anxiety or loss of interest in usual activities
• you are relying on caffeine, alcohol or stimulants to get through the day
• you are missing work or study because you feel unwell

If your fatigue is related to an acute winter illness and you need documentation for work or study, you may find Winter Sick Day? When Rest Beats Pushing On or Online Medical Certificates Australia useful.

Can you get a blood test referral online in Australia?

Yes, in many non-urgent situations, you can request a pathology referral through telehealth if a doctor decides it is clinically appropriate.

At NextClinic, our online blood tests service lets you complete a private online form, have your request reviewed by an AHPRA-registered Australian doctor, and receive a pathology referral online if approved. You can then take the referral to a pathology collection centre in Australia. Our doctors still make clinical decisions, which means they may recommend a different test, ask for more information, suggest an in-person assessment, or decline a referral if testing is not appropriate.

This can be useful if:

• your usual GP is booked out
• you have a known risk factor and want doctor-led advice
• you need a repeat test your doctor previously recommended
• you’re juggling work, family or study
• you want to discuss fatigue and whether blood tests make sense
• you need a pathology referral before a specialist appointment

We also discuss common blood tests and preventive health checks in Men’s Health Week: Blood Tests Men Often Skip, which may be helpful if you’re thinking beyond vitamin D and want to understand how doctors choose tests based on risk.

Telehealth is not the right setting for every situation. If you are acutely unwell, have severe pain, neurological symptoms, chest pain, severe breathlessness, fainting, signs of dehydration, or symptoms that need a physical examination, you should seek urgent in-person care.

A practical winter vitamin D checklist

If you’re unsure what to do next, start with this simple checklist.

1. Notice your symptoms Are you just a bit less energetic, or are you experiencing persistent fatigue, weakness, bone pain, muscle aches or falls?

2. Review your risk factors Think about skin tone, sun exposure, indoor work, shift work, clothing coverage, medical conditions, medications, pregnancy, breastfeeding, age, mobility, diet and previous vitamin D results.

3. Check your UV environment In northern Australia, sun protection may be needed year-round when UV is 3 or above. In southern Australia, there may be winter periods when short, sensible midday exposure is appropriate. Use the UV Index rather than guessing.

4. Avoid unsafe sun exposure Do not chase vitamin D by getting burnt. Sunburn is skin damage, not health optimisation.

5. Don’t self-prescribe high-dose supplements If you suspect deficiency, ask a doctor or pharmacist what dose is appropriate. If you have medical conditions or take other medicines, get advice first.

6. Ask whether a vitamin D blood test would change management This is the central question. If the answer is yes, a blood test referral may be worthwhile.

7. Follow up your result A pathology result is only useful if it leads to a clear plan. Ask what your level means, what to do next, and when to recheck if treatment starts.

So, do you need a vitamin D blood test this winter?

You might need one if you have risk factors, symptoms, bone health concerns, relevant medical conditions, or a doctor wants to guide treatment. You probably do not need one simply because it is winter and you are otherwise well.

The smartest approach is targeted, not automatic.

Vitamin D matters. Winter matters. But context matters too.

A vitamin D blood test can be very useful when it answers a specific clinical question: “Am I deficient, and what should we do about it?” A blood test referral is most appropriate when a doctor has assessed your symptoms and risk factors and decided testing is likely to guide care.

If you’re dealing with winter fatigue, don’t ignore it — but don’t assume vitamin D is the only explanation either. Look at your sleep, stress, mood, diet, recent infections, workload, menstrual history, exercise, medications and overall health. Then speak with a doctor about whether vitamin D testing, other blood tests or a different type of assessment is the right next step.

Bringing it all together

Here are the pivotal takeaways:

• Vitamin D deficiency is common in Australia, and rates rise in winter.
• A vitamin D blood test measures 25-hydroxy-vitamin D, usually reported in nmol/L.
• Routine screening of healthy adults is not generally recommended.
• Testing is most useful if you have symptoms, risk factors, bone health concerns or relevant medical conditions.
• Winter fatigue can have many causes, so a broader health review may be more useful than focusing on one vitamin.
• Safe sun exposure depends on the UV Index, your location, your skin type and your health history.
• Supplements can help, but high-dose vitamin D should not be taken without medical guidance.
• If clinically appropriate, we can help you request a doctor-led pathology referral online through NextClinic.

This week, choose one practical strategy: check the UV Index before your midday walk, write down your vitamin D risk factors, book a review for lingering fatigue, or ask your doctor whether a vitamin D blood test would actually change your care.

Which strategy will you try this week — and what did you notice? Share your choice or results in the comments.

References

• National Health Measures Survey, 2022-24 | Australian Bureau of Statistics
• Vitamin D test | healthdirect
• Vitamin D | Australian Bureau of Statistics
• Vitamin D | Cancer Council Australia
• Measuring vitamin D - Australian Prescriber
• Online Blood Tests & Pathology Referrals Australia

FAQs