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Get startedVitamin D: five things I've learned as a supplements expert
As resident nutrition and supplement expert at Which?, I've got the inside track on the vitamin D tips you need – and the mistakes to avoid
I've spent many hours analysing vitamin D supplements for Which? to uncover the best quality and value supplements you can buy – here are the key things I've learned that you need to know.
Generally, when it comes to supplements, I always warn that popping a handful of pills isn't a good substitute for a balanced diet.
Getting your vitamins and minerals from food is preferable. But if there's one supplement we should actually all be taking in the UK, it's vitamin D.
In fact, it's the only supplement that the NHS recommends everyone takes in the UK in winter months, and for a good reason: it's crucial for your health.
There are some things you need to know, from what is the right dose, to who needs more and why you shouldn't take too much. Get my top tips below or head straight to our Vitamin D supplement reviews for our top picks.
1. Don't rely on food alone for your vitamin D needs
When people ask me about what supplements they should take, my automatic response is: you can't out-supplement a poor diet, so don't just reach for a pill in the hope of an easy fix. But Vitamin D is the exception to this rule.
The primary source of Vitamin D is sunlight, which triggers its production in your skin. That’s why it’s crucial to supplement in winter: in the UK, and at similar latitudes, the sun's angle is just too low to produce sufficient Vitamin D between October and March.
This is an issue because Vitamin D plays numerous critical roles in the body. It’s crucial for calcium and phosphate absorption, which in turn are essential for strong bones, and it also plays a key role in immune-system regulation and muscle function.
And while there are some foods that naturally contain some Vitamin D – such as oily fish, egg yolks and fortified products (breakfast cereals, for example) – it's not enough to meet your daily needs.
2. Do consider alternatives to traditional tablets
Vitamin D is a fat-soluble vitamin, meaning that it needs fat for optimal absorption in the body.
While you can take a basic vitamin D tablet with a meal to aid this, I prefer the convenience and reliability of an oil-based capsule or a spray.
These formats already include the fat necessary for absorption, which means you don’t have to worry about taking them alongside food – instead, you can take them any time that suits your routine.
Vitamin D supplements come in plenty of different formats – from sprays and gummies to tablets and liquid drops. Sprays, drops and gummies can be really handy if you don't like swallowing pills or if you have digestive issues that impact absorption.
But not all products are made equal, and some have far fewer additives and unwanted extras than others. See our full vitamin D reviews for our recommended options, including the best value buys.
3. Do take it year-round if you have darker skin or tend to cover up
I take vitamin D throughout the year. That's because melanin, the pigment that makes my skin darker, makes it less efficient at synthesizing Vitamin D from the sun. So, even on bright summer days, I can't rely on sun exposure to provide enough (especially a UK summer!).
People with darker skin tones need a much greater level of sun exposure than those with paler skin to produce the same amount of Vitamin D, which would mean an impractical and potentially even dangerous amount of time spent in direct sunlight to get the same effect. So, boosting your Vitamin D levels year-round with a good quality supplement helps mitigate this.
4. Do give breastfed babies vitamin D, but skip it if using formula
A baby's bone development is dependent on Vitamin D, so it’s vital to make sure they have enough. The NHS recommends that breastfed babies should have a daily vitamin D supplement of 8.5-10mcg – equivalent to 400IU (international units) – from birth, and it’s important to note that that is the case even if you are taking a vitamin D supplement yourself.
Bottle-fed babies having more than 500ml of infant formula milk a day don’t need an additional supplement, because baby formula already contains vitamin D. If you are mixed feeding, don’t supplement unless your baby’s formula intake is less than 500ml.
Although severe vitamin D deficiency is relatively rare in the UK, a 2022 government report found almost one in five children have low vitamin D. You can find out more in our guide to vitamin D supplements for babies and children.
5. Don't overdo it – more isn’t necessarily better
Official NHS guidance recommends adults take 10mcg (micrograms) of vitamin D daily to avoid deficiency, but many widely available high street supplements contain higher doses.
The most common dosage level you'll find is 25mcg, equivalent to 1,000IU. This is probably because lots of people in the UK are likely to be deficient in vitamin D, so manufacturers have played it safe with a higher dose.
Taking up to 50mcg a day is generally considered to be safe, but most people are unlikely to need more on a regular basis. Don't be tempted by super-high doses; more is not better and taking too much vitamin D over a long period can cause health issues. This is because it's fat soluble, which means it can build up in your body and can cause calcium to do the same. This can actually weaken bones and damage your heart and kidneys, and is known as hypercalcaemia.
The maximum upper safe limit recommended by the NHS is 100mcg, but most people don't need anything like this much and it's not something to aim for. Be aware that vitamin D is frequently added to other supplements, as well as some food and drink (especially cereals, smoothies and health drinks).
If you are extremely deficient in vitamin D, then you might be prescribed a higher weekly dose by your GP for a short period, but this is usually supervised and only implemented when medically necessary.
Best multivitamin supplements – in need of an all-rounder? See our independent expert reviews, which rate each product for the amount of fillers and additives, as well as dose and bioavailability
Shefalee Loth, Which? principal researcher and nutritionist
Shefalee is a public health nutritionist with over 20 years' experience, and has worked for the NHS, The London School of Hygiene & Tropical Medicine and World Cancer Research Fund, as well as for many years at Which? overseeing our nutrition and supplements content.
Shefalee is the research lead for our health and wellbeing reviews, and a principal researcher – one of our most experienced in-house researchers. She has written a wide range of investigative and reviews-based food, health and nutrition content for our magazine and website. She is also a Which? media spokesperson, and a trustee at Sustain, the food and farming alliance.
Shefalee focuses on cutting through the hype to explain what you need to know about nutrition and healthy eating, and to help you choose better. From 'How bad is ultra-processed food?' to the 'Top gut health myths you need to know about' and 'What really works to cut cholesterol', she gives no-nonsense advice to help you make healthier choices and save money.
