Vitamin D: who actually needs a supplement?

Vitamin D is one of the most popular supplements, and testing for it has become almost routine. But does everyone need a supplement and a test? In 2024, the Endocrine Society, one of the leading medical societies in endocrinology, published a new guideline on the topic ^[1]. Its answers surprised many people.

Why vitamin D matters

Vitamin D helps the body absorb calcium and is needed for healthy bones and muscles. The body makes it in the skin when exposed to sunlight, and we get small amounts from food, mainly oily fish, egg yolks and fortified foods ^[2]. In the winter months the sun is weak and skin production drops considerably.

What the 2024 guideline recommends

The guideline covers people who do not already have a specific medical reason to take vitamin D or to be tested, and looks at when extra vitamin D lowers the risk of disease ^[1].

1. No routine testing in healthy people

The experts advise against routinely measuring vitamin D levels (25(OH)D) in healthy people ^[1]. The reason: there is no evidence that testing and then treating to a target level improves health in these groups.

2. Extra vitamin D for specific groups

Intake above the standard recommendation is suggested for ^[1]:

• children and teenagers (1 to 18 years), to prevent rickets and possibly lower the risk of respiratory infections;
• pregnant people;
• adults over 75;
• adults with prediabetes, alongside lifestyle changes.

3. Healthy adults under 75

For this group, the guideline does not recommend intake above the standard daily recommendation ^[1]. In other words, more vitamin D does not mean more benefit if your intake is already enough.

How much vitamin D per day?

These figures come from the US National Institutes of Health Office of Dietary Supplements ^[2]. The safe upper limit for adults is 4,000 IU (100 mcg) per day ^[2]. Vitamin D is stored in body fat, so very high doses over a long time can be toxic.

What this means for you

• Don't start mega-doses "just in case". If you are healthy and under 75, a standard dose in winter is usually enough.
• Include foods with vitamin D: salmon, mackerel, sardines, eggs and fortified dairy.
• If you are in one of the higher-need groups, talk to your doctor about the right dose.
• Testing makes sense when there is a specific medical reason, such as a condition that affects absorption or symptoms your doctor wants to check.

If you want a meal plan that covers your vitamins and minerals mainly from food, see how the personalised meal plan works.