Vitamin D Deficiency
Vitamin D helps your body use calcium to keep bones and muscles strong. Most of it is made in your skin from sunlight. Low levels are common and easy to fix, but extra vitamin D on top of normal levels won’t make you live longer.
The vitamin D ladder
Most people with normal risk get enough from a little sun. People at higher risk, or with low levels, add a daily supplement. Bigger doses are only for proven deficiency.
- Step 1 · Self-careA little safe sunIn summer in Australia, a few minutes of mid-morning or mid-afternoon sun on your arms and hands most days. In winter in southern states, time outdoors around midday with some skin uncovered.
- Works
- Enough for most people at normal risk
- Cost
- Free
- How long
- Ongoing, adjusted for season
- Watch for
- Longer sun doesn’t raise vitamin D further, just your skin cancer risk. Use sun protection when the UV index is 3 or above and you’ll be out for more than a few minutes
You need minutes, not a tan.
- Step 2 · Self-careFood sourcesOily fish (salmon, sardines, mackerel), eggs, and foods with added vitamin D such as some milks, spreads and cereals.
- Works
- Helps, but it’s hard to get enough from food alone
- Cost
- Your usual grocery bill
- How long
- Ongoing
- Watch for
- Food alone rarely fixes a true deficiency
Food is the side dish. Sunshine is the main.
- Step 3 · PharmacyDaily vitamin D3 supplementFor mild deficiency (30–49 nmol/L), or year-round if you’re at higher risk and can’t get safe sun: usually 1,000–2,000 IU a day for adults.
- Works
- Brings levels up over about 3 months. Combined with calcium, cuts hip fractures by about 15% in older people, mostly in aged care
- Cost
- About $10–20 for several months
- How long
- Often ongoing for at-risk groups; recheck after 3 months if you were low
- Watch for
- More isn’t better. Don’t exceed 4,000 IU (100 micrograms) a day unless a doctor advises it
Daily and boring beats big and occasional.
- Step 4 · Doctor-guidedHigher doses for moderate or severe deficiencyFor levels under 30 nmol/L: usually 3,000–5,000 IU a day for adults for 6–12 weeks, then a maintenance dose.
- Works
- Corrects deficiency reliably; bone pain and muscle weakness from deficiency improve over weeks to months
- Cost
- About $10–30
- How long
- Weeks, then a lower ongoing dose and a recheck at about 3 months
- Watch for
- Children, pregnancy and breastfeeding have their own doses: follow your doctor’s plan
A fix with a finish line, then a maintenance plan.
- Step 5 · SpecialistLooking for a hidden causeWhen levels stay low despite supplements, or with bone softening, rickets or abnormal calcium. Causes include coeliac disease, bowel disease, weight-loss surgery, kidney or liver disease and some medicines.
- Works
- Treating the cause often fixes the vitamin D too
- Cost
- Public is free (with waits); private specialist fees vary, with Medicare rebates on referral
- How long
- Depends on the cause
- Watch for
- Some seizure medicines and rifampicin lower vitamin D
If topping up doesn’t fill the tank, look for the leak.
Save your money
Popular, heavily marketed or often asked about, but the evidence is weak or says no.
- High doses for everyone to prevent cancer, heart disease or early deathAn Australian trial of 21,315 people aged 60 and over found monthly vitamin D didn’t help them live longer. Good for bones when low; not a longevity pill.
- Vitamin D to stop colds and fluA 2025 analysis of 49 trials with over 60,000 people found no clear protection against chest and throat infections.
- Once-a-year mega-dosesOne large trial found a single big yearly dose increased falls and fractures in older women. Regular modest doses are safer.
- Routine testing in healthy peopleNot recommended. In Australia, Medicare covers the test only for people at higher risk.
- Vitamin D injections and IV dripsTablets or liquid work for nearly everyone and are far cheaper.
What you can do
- Get outdoors in daylight most days, with sensible sun protection when the UV index is 3 or above.
- If you’re at higher risk (see below), talk to your GP about a daily supplement rather than waiting for a test.
- Take vitamin D with a meal that has some fat in it. It’s fat-soluble.
- Look after the rest of your bone health: calcium-rich food and strength exercise. See our osteoporosis sheet.
- Outside Australia, check local advice. In the UK, everyone is advised to consider 10 micrograms (400 IU) a day in autumn and winter.
See your GP if
- You’re at higher risk: dark skin, little time outdoors (housebound, in residential care, night shift), covering most of your skin outdoors, a body mass index over 30, or conditions that affect absorption such as coeliac or bowel disease
- You have bone pain, muscle weakness (such as trouble getting out of a chair) or have broken a bone from a minor fall
- You’re pregnant or breastfeeding with risk factors
- Your baby is exclusively breastfed and you have risk factors or low vitamin D yourself
See a doctor the same day if you take high-dose vitamin D and develop severe thirst, frequent urination, vomiting, confusion or weakness: signs of too much calcium. Call 000 (or your local emergency number) for a baby or child with a seizure or muscle spasms, which can happen with very low calcium.
Common questions
What level counts as low vitamin D?
Australian guidance: 50 nmol/L or more is adequate. 30–49 is mild deficiency, 12.5–29 moderate, and under 12.5 severe. Levels may be best kept at 75 or more with osteoporosis. Your level is often a little lower at the end of winter.
What are the symptoms of low vitamin D?
Usually none. Severe or long-lasting deficiency can cause bone pain and tenderness, muscle weakness and aches, and bone softening (osteomalacia in adults, rickets in children, with bowed legs and delayed growth).
Who is at risk of low vitamin D?
People with dark skin, those who get little sun (indoor or night-shift workers, people who are housebound or in residential care, or who cover their skin), people with a higher body weight, people with coeliac disease, bowel disease, kidney or liver disease, or after weight-loss surgery, and exclusively breastfed babies of mothers with low vitamin D.
Should everyone take a vitamin D supplement?
Not in sunny countries if you get regular safe sun. People at higher risk usually do best with a daily supplement. In the UK, where sunlight is weak from October to March, everyone is advised to consider one in autumn and winter.
Can you have too much vitamin D?
Not from the sun, but yes from supplements. Too much raises calcium, which can harm the kidneys, heart and bones. Adults shouldn’t exceed 4,000 IU (100 micrograms) a day unless a doctor advises it. Blood levels above 125 nmol/L are best avoided.
Do babies need vitamin D drops?
In Australia, breastfed babies at higher risk (for example, if their mother has low vitamin D or dark skin) are usually given 400 IU a day for the first year. In the UK, all breastfed babies are advised to have 8.5–10 micrograms a day. Formula already contains vitamin D.
Helpful resources
- Cancer Council: How much sun is enough?Plain-English guide to getting vitamin D without overdoing the sun, by season and city. Free, Australia.
- NHS: Vitamin DUK supplement advice for adults, children and babies, plus safe upper limits. Free.
Evidence and more information
- Tasmanian Department of Health: Low vitamin D, testing and treatment guidelines (2024)
- Cancer Council Australia: How much sun is enough?
- NHS: Vitamin D
- Lancet Diabetes and Endocrinology (2022) summary: D-Health trial, vitamin D and mortality
- Lancet Diabetes and Endocrinology (2025) summary: vitamin D and respiratory infections
- Cochrane: Vitamin D and calcium for preventing fractures (2014)
maladywise.com/vitamin-d/