Vitamin D deficiency in women: symptoms, the blood test and Australian ranges.

Vitamin D deficiency is checked with a single blood test, 25-hydroxy vitamin D, reported in nmol/L. In Australia a level of 50 nmol/L or above is considered sufficient, with lower bands for mild, moderate and severe deficiency. Despite the sun, low levels are common in Australian women, especially at the end of winter in the southern states.

Why vitamin D is checked in women

Vitamin D is really a hormone your skin makes from sunlight, and its main job is helping your gut absorb calcium so bone can be built and maintained. It turns up often in women's health.

• Bone health: women lose bone faster after menopause, so vitamin D is a standard part of a postmenopausal baseline alongside calcium and parathyroid hormone.
• Pregnancy and preconception: the baby's skeleton draws on your supply, and low levels are common in pregnancy, so it is checked before or early in pregnancy.
• Postpartum: months indoors with a newborn, feeding and disrupted routines often leave stores low at exactly the time exhaustion is dismissed as normal.
• Fatigue and low mood: low vitamin D is one of the checkable causes on the tiredness shortlist, next to iron and thyroid.
• Hair shedding: it sits in most hair loss panels because low levels are common in women who shed, though the link is still being studied.

Symptoms of low vitamin D

The honest answer to "how do I tell if my vitamin D is low" is that usually you cannot, from symptoms alone. Mild and moderate deficiency is often silent, and the symptoms it does produce are shared with a dozen other things. These are the ones most often reported.

• Tiredness that does not match your sleep
• Aching bones, particularly the lower back, hips and ribs
• Muscle aches or weakness, and difficulty climbing stairs or rising from a chair
• Low mood, especially through winter
• Possibly more frequent minor infections, although the evidence here is mixed
• Hair shedding
• In severe or long-standing deficiency, bone pain and fractures from minor falls

None of these is specific, so symptoms point you towards a test rather than giving you the answer.

The 25-hydroxy vitamin D test and Australian ranges

On a blood test vitamin D is called 25-hydroxy vitamin D, often written 25-OH D or 25(OH)D. It is the storage form in your blood and reflects the vitamin D your skin has made plus any taken in through food over the previous several weeks. Australian laboratories report it in nanomoles per litre (nmol/L); an overseas result in ng/mL is multiplied by 2.5 to compare.

Ranges vary by laboratory; your report shows the range your lab uses. The categories above follow the Australian and New Zealand position statement on vitamin D (2012), which Australian laboratories and Healthdirect still use.

Medicare rules: when a GP can and cannot bulk bill it

Until 2014, vitamin D was one of the most frequently ordered blood tests in Australia, and Medicare-funded testing had grown many times over in a decade. From 1 November 2014 the Medicare Benefits Schedule restricted the rebate to people who meet defined criteria. Broadly, a GP can request a rebated vitamin D test if you have signs or symptoms of osteoporosis or osteomalacia, a raised alkaline phosphatase, a parathyroid or calcium disorder, a condition affecting absorption, chronic kidney disease, deeply pigmented skin or very limited sun exposure for medical or cultural reasons, take medicines known to lower vitamin D, or are an infant whose mother is deficient, or a child whose sibling has deficiency. Feeling tired, on its own, is not one of the criteria.

If none of those apply, for example you are a healthy woman who feels tired and wants to know her level, the test is not rebated and a GP either cannot bulk bill it or asks you to pay privately. That is the gap self-pay testing fills: no referral, you pay the test price, and the result comes to you in plain English.

Sun, season and skin: why levels drop in winter in the southern states

Your skin makes vitamin D from UVB in sunlight, and the UV index has to be reasonably high for that to happen efficiently. In Melbourne, Hobart, Adelaide and southern New South Wales the winter UV index is often too low for much production, so levels fall from autumn, bottom out around August and September, and recover over summer. Brisbane and Darwin see less of a swing.

Other things push levels down: days spent indoors, covering skin for cultural or medical reasons, darker skin (which needs more sun for the same production), higher body weight, gut conditions that affect absorption, and the sun protection Australians are rightly taught to use. Balancing skin cancer prevention against vitamin D is a conversation for your doctor, not a reason to skip sunscreen.

Your KnowLuna vitamin D result

The KnowLuna vitamin D test measures 25-hydroxy vitamin D from a single blood sample, collected at an accredited centre near you or with a home kit or a nurse visit if you prefer. No fasting, any time of day. Your report shows your level in nmol/L against the categories above with a plain-English note, and any moderate or severe result is followed up by a doctor. What to do about a low level depends on how low it is and why, and is a conversation for your doctor.

Common questions

Sources and further reading

• Medical Journal of Australia: Vitamin D and health in adults in Australia and New Zealand, position statement (2012)
• Medicare Benefits Schedule: item 66833, vitamin D testing criteria
• Healthdirect: vitamin D deficiency
• Healthdirect: vitamin D test
• Better Health Channel: vitamin D

General information only, not medical advice. If your symptoms are severe or sudden, see a doctor promptly. This page does not replace a consultation with a doctor who knows your history; read our medical disclaimer.