Taking vitamin D supplements is not recommended for most New Zealanders. It is only helpful for some people at risk of vitamin D deficiency.
Do I need a vitamin D supplement?
Taking vitamin D supplements is not recommended for most New Zealanders. It is only helpful for some people at risk of deficiency. You have increased risk of deficiency if you:
- are housebound with limited exposure to direct sunlight, such as frail older people
- have dark-coloured skin
- completely cover your skin with clothing or veils
- completely avoid the sun for medical reasons, eg, because you have had skin cancer or are using medicines that sensitise you to the sun
- live in southern regions of New Zealand, which means you may experience some vitamin D deficiency during the winter months between May and August, when there are fewer sunlight hours
- are receiving treatment for osteoporosis and need to take calcium supplementation because you are not getting enough calcium in your diet (vitamin D helps your body to absorb calcium).
Note: Only some of the people listed above need vitamin D supplements.
Why should I consult my doctor before starting supplements?
If you think you are at risk of vitamin D deficiency, talk to your doctor before taking supplements. Taking supplements under the care and advice of your doctor helps ensure you are getting the full benefit of the supplements. It also reduces the risk of harm that can occur from taking too much vitamin D.
Your doctor or pharmacist can also check for any interactions between other supplements and medications.
Is there more than one form of vitamin D?
There are 2 main forms of vitamin D:
- ergocalciferol (also known as vitamin D2)
- cholecalciferol (also known as vitamin D3).
Vitamin D3 is more potent than vitamin D2. Vitamin D3 is the natural form that is made in your body when you are exposed to sunlight. Vitamin D2 is available in some foods and also in supplements that often require a doctor’s prescription.
Which supplement should I take and how much do I need?
If your vitamin D levels are low, your doctor may recommend vitamin D3 (colecalciferol) 1.25 mg (50 000 IU) once a month.
Your doctor will ask about your diet. Calcium helps your body to absorb vitamin D, so you need to make sure you are getting enough calcium in your diet – but not too much. Your doctor or pharmacist can advise you about this.
If you are at risk of more severe vitamin D deficiency, you will need higher doses of vitamin D supplements (colecalciferol). Examples of such conditions include:
- those that mean you don't absorb nutrients from your gut well, eg, Crohn's disease or coeliac disease
- chronic liver disease
In chronic kidney disease, damage to your kidneys affects the metabolism of vitamin D. People with severe kidney disease may require vitamin D supplements such as alfacalcidol (One alpha®) or calcitriol (Calcitriol-AFT®), and other supplements such as calcium.
Do I need a vitamin D test?
Your doctor may recommend a vitamin D test if you are at a very high risk of vitamin D deficiency. A test is not always needed before your doctor prescribes a vitamin D supplement and is generally not needed for monitoring your levels if you are taking vitamin D.
Read more: Do I need a vitamin test? Choosing Wisely, NZ
Can I get too much vitamin D?
Yes, you can get too much vitamin D, but it is very rare. It can happen if you take high levels of vitamin D supplements over a long period of time.
If you do this, you may be at risk of adverse effects, such as headaches and stomach upset, kidney stones, kidney failure and abnormal heart rhythms. For this reason, you should only take vitamin D as recommended and prescribed by a doctor.