Some multivitamin brands may be giving shoppers a false sense of security over their Vitamin D intake, experts have warned.

A Daily Mail analysis has found that dozens of supplements on sale in Britain contain well below the levels recommended for adults – despite some labels suggesting they provide '100 per cent' of daily requirements.

The NHS advises adults and children over four to consider taking a daily 10 microgram (mcg, sometimes written as µg) Vitamin D supplement during autumn and winter, when sunlight exposure is limited.

Vitamin D, often called the 'sunshine vitamin', is produced in the skin through sunlight exposure and is also found in foods such as oily fish, eggs and fortified cereals. It plays a vital role in regulating calcium and phosphate, helping to maintain healthy bones, teeth and muscles.

However, supplement labels are still based on a European nutrient reference value (NRV) of 5mcg, a figure set decades ago that is now only half the UK's recommended intake.

This means products containing 5mcg can legally be labelled as providing '100 per cent' of daily Vitamin D, even though they deliver just 50 per cent of current government guidance.

Dietitian Dr Carrie Ruxton, from the Health & Food Supplements Information Service (HSIS), said the mismatch risks confusing consumers.

'We've got this really strange anomaly in labelling law where the NRV comes from older European regulations and doesn't match current UK recommendations,' she said.

'People may discover they are low in vitamin D, buy a supplement and see that it contains 100 per cent of their intake and assume that's enough.

'In reality, 5mcg is only half of what the UK Government recommends. The NRV for Vitamin D is out of date and needs to double.'

Most labels on popular brands of multivitamins available from high street pharmacies reviewed by the Daily Mail continue to use the older NRV system. 

Many of the lowest–dose products are gummy supplements, while the number of capsules or gummies recommended per serving also varies, adding further confusion for shoppers.

One product, Nutriburst Health and Vitality Vitamin Gummies, contains just 1.5mcg Vitamin D per serving of two gummies, equivalent to 15 per cent of the UK recommendation.

The nutritional information for this product on the Boots website states that the supplements contain 30 per cent of the NRV. 

Boots Multivitamin Gummies provide 5mcg per serving, while two products by Health & Her contain 2.5mcg per serving.

On the packaging of the Boots Multivitamin Gummies, it states that per gummy, there is 5mcg of Vitamin D3 and '100 per cent' of the NRV. 

For both Health & Her products, the nutritional label says that two tablets 'typically provide' 2.5mcg of Vitamin D3, 50 per cent of the NRV.

Even where products do contain higher amounts, serving sizes differ. 

Some brands require multiple gummies or capsules to reach their stated dose, meaning consumers must check instructions carefully to understand how much they are actually getting.

At the other end of the spectrum, the Daily Mail's analysis identified one multivitamin containing 45mcg of vitamin D per serving, well above daily guidance but still below the UK's safe upper limit.

Some supplements use Vitamin D2, also known as ergocalciferol, rather than Vitamin D3, cholecalciferol, which is generally considered more effective at raising Vitamin D levels in the blood.

Excessive Vitamin D intake can, in rare cases, lead to toxicity, causing high calcium levels, kidney problems, nausea, weakness and confusion. However, this is typically linked to high dose supplements rather than diet or sunlight exposure.

In practice, many popular multivitamins provide only half, or even less, of the Vitamin D adults are advised to take daily in the UK, despite claiming to provide up to 100 per cent of the daily requirement.

Food supplements sold in England are regulated but they are not treated as medicines.

Under the Food Supplements (England) Regulations 2003, products must be clearly labelled as 'food supplements'. Labels must include key information such as the ingredients, the recommended daily intake, and the name and address of the business responsible for the product.

There are also required safety warnings. Labels must state that the recommended daily dose should not be exceeded, that the product should be kept out of reach of young children, and that supplements should not be used as a substitute for a varied, balanced diet.

If a supplement contains vitamins, minerals or other substances with a nutritional or physiological effect, the label must show the amount of each so consumers know what they are taking.

There are strict limits on what companies can claim. Supplements cannot be marketed as preventing, treating or curing disease. 

Any health claims must comply with the UK Nutrition and Health Claims Regulation and be authorised.

Unlike medicines, there is no single set of fixed legal maximum levels for all vitamins and minerals in supplements across the UK. Instead, safety is assessed using scientific guidance, and regulators can take action if a product poses a risk.

Following Brexit, the UK retained these rules in domestic law, with responsibility now sitting with UK authorities rather than EU institutions.