Whether you want to support your immune system ahead of cold and flu season, are worried about your bone health or simply want to keep your energy levels up throughout autumn and winter, vitamin D is one of those supplements that seems to do it all.

While experts have long raved about the benefits of vitamin D – the NHS recommends every adult in the UK takes some form of vitamin D supplement between October and March – the pandemic brought it to the forefront of the public consciousness, after research suggested that vitamin D supplementation could potentially reduce the severity of a Covid-19 infection. 

With vitamin D supplements now available in tasty spray and gummy forms, it’s easier than ever to ensure you’re getting plenty of vitamin D all year round. However, just because vitamin D is essential for our health, doesn’t mean there isn’t a limit to how much we should take. 

The NHS recommends that adults and children over four years (including pregnant and breastfeeding women) should consider taking a daily supplement containing 10 micrograms (400 IU) of vitamin D during autumn and winter.

It’s also recommended that certain groups take a daily supplement containing 10mcg of vitamin D all year round. These include people who are not often outdoors (for example, if they’re frail, housebound or live in a care home) or usually wear clothes that cover up most of their skin.

Darker skin can also make it difficult to make enough vitamin D from sunlight (even if you spend lots of time outside), so it’s recommended that people from an African, African-Caribbean or South Asian background also take a daily 10mcg supplement.

While there are foods which contain vitamin D, most people will find it difficult to get enough vitamin D from their food alone, which is why supplementation is recommended. 

While 10mcg or 400IU of vitamin D is the amount most people will need daily, you might have noticed some supplements contain a much larger dose – up to 4000 IU.

According to Boots nutritionist Vicky Pennington, however, most people won’t need these dosages – often advertised as ‘max strength’. “Normal strength vitamin D should be sufficient for most of the population,” she says. “Do not take more than 100mcg a day.”

This upper limit applies to adults, including pregnant and breastfeeding women and the elderly, as well as children aged 11-17 years. For children aged 1-10, the upper limit is 50mcg or 2000 IU a day, while infants under 12 months should not have more than 25mcg or 1000 IU.  

These upper limits mean it’s important to be aware of the dosage directions for your specific supplement – if it says two sprays per day, for example, that will deliver the dose on the packet. If you’re taking a selection of supplements, you also need to be aware of the total amount of vitamin D you’re taking – if one supplement contains 1000 IU and the other 4000 IU, then you could end up taking too much vitamin D without realising it.

There may be some cases where people are advised to take more vitamin D than the upper limit by their doctor – for example, those with conditions that affect vitamin D absorption. But unless told otherwise, you should limit your consumption to 4000 IU or lower.

Supplements aside, it’s not possible to overdose on vitamin D from sun exposure alone, and most people will struggle to get enough vitamin D from their diets – let alone get too much.

However, Pennington adds: “While you can’t overdose on vitamin D from sunlight, always protect your skin during prolonged sun exposure to prevent skin damage and reduce the risk of skin cancer by following sun safety guidelines.” 

Taking too much vitamin D can have ramifications for your health, which is why it’s so important to watch how much you’re taking on a daily basis.

This is because vitamin D is a fat-soluble vitamin, which makes it harder for our body to easily excrete any excess. Over time, this means vitamin D levels can build up in the body.

“Taking too many vitamin D supplements over a long period of time can cause too much calcium to build up in the body, which is known as hypercalcaemia,” Pennington explains. “This can weaken the bones and damage the kidneys and heart.”

According to the NHS and Mayo Clinic, symptoms of hypercalcaemia include:

• Being sick
• Drowsiness
• Frequent urination
• Weakness
• Dehydration
• Confusion
• Muscle spasms
• Bone pain
• Joint pain
• Irregular heartbeat

If you’re concerned you might have taken too much vitamin D, you should seek medical advice. However, hypercalcaemia is rare – especially if you don’t go overboard with the vitamin D.

In general, a good way to work out whether your vitamin D supplementation is having the desired effect is to take a vitamin D test. Indeed, as nutritionist Thalia Pellegrini previously told Strong Women: “I always recommend doing a vitamin D test once or twice a year. They’re inexpensive, easy to do at home and you can know how much vitamin D you actually need.” 

Images: Getty