Patient Guide
Low Vitamin D
What it does, who's at risk, and how we treat it
Sunlightmakes most of your vitamin D — only a little from food
Often nonelow vitamin D usually causes no symptoms at all
50+the blood level (nmol/L) usually targeted
Mostly made by your skin — not found in your diet. Vitamin D keeps your bones and muscles strong. In Australia, the trick is getting enough sun safely — without raising your skin cancer risk.
Who's more likely to be low?
Little sun exposure
Spending most of your time indoors, working office hours or night shifts, or rarely getting outside.
More likely if: indoor work, shift work, or you're largely housebound.
Darker or covered skin
More melanin, or skin that's mostly covered for cultural or religious reasons, means less vitamin D made per minute of sun.
More likely if: a darker skin tone, or skin that's routinely covered.
Older age
Skin becomes less efficient at making vitamin D as we get older.
More likely if: you're aged over 65.
Higher body weight
Vitamin D is fat-soluble and gets held in body fat, leaving less available in the blood.
More likely if: a higher BMI.
Gut absorption problems
Coeliac disease, Crohn's disease or bariatric surgery can all reduce how much vitamin D your gut absorbs.
More likely if: coeliac disease, inflammatory bowel disease, or previous bariatric surgery.
Pregnancy & babies
Breastfed babies of mothers with little sun exposure get very little vitamin D through milk alone.
More likely if: you're pregnant or breastfeeding, or have a breastfed baby with little sun exposure.
Does everyone need a blood test? No — testing isn't a routine check for everyone. It's generally reserved for people with symptoms or one of the risk factors above. We test 25-OH vitamin D, and in Australia a level of 50nmol/L or more is usually the target, with some margin for the seasonal dip over winter.
Three ways to top it up
1
Safe sunlight
Often just a few minutes most days via everyday activities — your main source
2
A few foods
Oily fish, eggs, and milk or cereal fortified with vitamin D — rarely enough alone
3
A supplement
Usually a daily vitamin D3 — your GP advises the dose and how long
Getting sun safely — the Australian balance
UV 3 or above (most of the year)
- A few minutes most days via everyday activities is usually enough
- Protect your skin the rest of the day — sunscreen, a hat or shade
- No deliberate sunbaking — more sun doesn't mean more vitamin D, and it raises skin cancer risk
- Darker skin generally needs a little longer in the sun
UV under 3 (cooler months)
- Spend a little longer outdoors around the middle of the day
- Uncovering some skin, like your arms, can help when practical
- Sun protection generally isn't needed for short periods under UV3
- Southern Australia's winter sun is weak — a supplement is often more reliable
Good to know
More isn't better — very high doses taken long-term can raise your calcium levels and cause harm, so stick to the dose your GP advises. Tell your GP about any other health conditions first, and expect a recheck a few months after starting, since levels take time to recover.
Low Vitamin D Is Common — And Easily Fixed
Safe sun and the right supplement mean stronger bones and muscles. We'll check your level, sort the cause, and recheck in a few months.
— Dr Regu
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