Vitamin D supplements for adults

If you think you need a vitamin D supplement, talk to your doctor before taking one. Taking supplements under the care and advice of your doctor helps ensure you are getting the full benefit. It also reduces the risk of harm that can occur from taking too much vitamin D. Taking too much vitamin D over a long period of time can cause too much calcium to build up in the body (hypercalcaemia). This can weaken the bones and damage the kidneys and the heart.

Your doctor or pharmacist can also check for any interactions between supplements and other medicines you may be taking. 

As mentioned above, vitamin D supplements are not usually required unless you are at risk of vitamin D deficiency. Vitamin D is sometimes included in multivitamin supplements. If you choose to take vitamin D supplements, 10 micrograms a day will be enough for most people.

Do not take more than 100 micrograms (4,000 IU) of vitamin D a day as it could be harmful. This applies to adults, including pregnant and breastfeeding women and the elderly, and children aged 11–17 years. See how much vitamin D you need and if you can get too much of this vitamin here.

Some people are at risk of more severe vitamin D deficiency, and need higher doses of vitamin D supplements (colecalciferol) because of having specific health conditions. Examples include:

• conditions where you don't absorb nutrients from your gut well, eg, Crohn's disease or coeliac disease
• chronic liver disease
• hypoparathyroidism.

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.

Your doctor may recommend a vitamin D test if you are at a very high risk of vitamin D deficiency, but it's not always needed. A test is generally not needed for monitoring your levels if you are taking vitamin D.

Read more about whether you need a vitamin test.(external link)

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. 

There is some evidence of an association between vitamin D deficiency and increased severity of COVID-19. However, vitamin D supplementation is only recommended for people with vitamin D deficiency, or those at risk of deficiency, such as older people who are frail, housebound or living in residential care, people with dark skin pigmentation or people with obesity, chronic kidney disease, liver failure or another medical condition that affects vitamin D metabolism.