Vitamin D Tablets This Winter: How Much to Take, Which to Buy, and Who Needs Them All Year

Every October the vitamin D questions start. "Which one should I get?" "Is 1,000 better than 400?" "My daughter says I should be on 4,000." The supplement shelf does not help: drops, sprays, gummies, capsules and tablets, in strengths labelled in two different units. The good news is that the actual NHS advice is short and simple, and once you know it, picking a product takes about thirty seconds.

Why do we need vitamin D in winter?

Vitamin D helps the body control calcium and phosphate, which keep bones, teeth and muscles healthy. A long-term lack of it can cause rickets in children and bone pain from osteomalacia in adults.

Most of our vitamin D is made in the skin from sunlight. According to the NHS vitamin D page, from about late March to the end of September most people can make all they need. But between October and early March, the sun in the UK is not strong enough for the body to make enough, and food alone rarely makes up the gap. Oily fish, red meat, egg yolks and fortified foods contain some, but UK cows' milk is generally not fortified, so it is not a good source.

That is why the government advice is that everyone should consider a daily vitamin D supplement during autumn and winter.

How much vitamin D should I take per day?

For adults and children aged 1 and over, the NHS recommends 10 micrograms a day. That includes pregnant and breastfeeding women and people at risk of deficiency. Babies under 1 need 8.5 to 10 micrograms a day.

Micrograms and IU: reading the label

Labels use two units, which is where most of the confusion at our counter comes from. The NHS conversion is simple: 1 microgram equals 40 IU. So:

• 10 micrograms = 400 IU (the recommended daily amount)
• 25 micrograms = 1,000 IU
• 100 micrograms = 4,000 IU (the safe upper limit for adults)

A vitamin D 1000 IU tablet is therefore 25 micrograms, two and a half times the recommended daily amount but well under the adult upper limit. It is a safe choice for most adults if that is what you have, but the NHS says 10 micrograms a day is enough for most people, so you do not need to pay for a higher strength.

The upper limits

The NHS says do not take more than:

• 100 micrograms (4,000 IU) a day for adults, including pregnant and breastfeeding women and older people, and children aged 11 to 17
• 50 micrograms (2,000 IU) a day for children aged 1 to 10
• 25 micrograms (1,000 IU) a day for babies under 12 months

Taking too much over a long time can cause calcium to build up in the blood (hypercalcaemia), which can weaken bones and damage the kidneys and heart. You cannot overdose on vitamin D from sunlight. If a doctor has prescribed you a different dose, follow their advice instead.

Who needs vitamin D all year round?

The Department of Health and Social Care recommends a daily 10 microgram supplement throughout the year, not just in winter, for adults and children over 4 who:

• are not often outdoors, for example because they are frail or housebound
• live in a care home
• usually wear clothes that cover most of their skin when outdoors

People with dark skin, for example from an African, African-Caribbean or South Asian background, may also not make enough vitamin D from sunlight and should consider a daily supplement all year. Medway is a diverse community, and this is the group I most often find has never been told.

For babies and young children:

• breastfed babies need a daily supplement of 8.5 to 10 micrograms from birth
• formula-fed babies do not need one while they are having 500ml (about a pint) or more of infant formula a day, because formula is already fortified
• all children aged 1 to 4 should have 10 micrograms every day, all year

What is the best vitamin D supplement?

There is no single best brand. The best supplement is the one at the right dose that you will actually take every day. When people ask me, I go through four questions:

• Is the dose right? For most adults, 10 micrograms (400 IU) is enough. Anything up to 25 micrograms (1,000 IU) is fine. Avoid high-strength products unless a doctor has advised them.
• Which form will you remember? Tablets, capsules, chewables, drops and a vitamin D spray all deliver vitamin D. A spray or chewable can suit people who struggle to swallow tablets. Drops are the usual choice for babies and toddlers.
• Does it suit your diet? Some capsules contain gelatine, which is not suitable for vegetarian, vegan, halal or kosher diets. Vegan vitamin D products exist, so check the label or ask us.
• Do you have a nut or soya allergy? The NHS advises telling a doctor before taking colecalciferol if you have a peanut or soya allergy. Check the ingredients, or ask the pharmacist to check them for you.

Who should check before taking vitamin D?

The NHS guidance on colecalciferol, the most common form of vitamin D, lists people who should speak to a doctor first. That includes anyone with high calcium levels in the blood or urine, kidney problems or kidney stones, sarcoidosis, or high vitamin D levels already.

It can also interact with other medicines. The NHS lists medicines to mention before you start, including digoxin for the heart, "water tablets" such as bendroflumethiazide or indapamide, some epilepsy medicines, and steroids such as prednisolone. Many of our older patients take one of these, which is why we ask what else you take before recommending a product.

The mistake I see most often

A woman in her late 60s brought a basket to the counter last November: a 4,000 IU vitamin D tablet her son had recommended, a multivitamin, and a question about whether she should keep taking her calcium and vitamin D tablets from the GP. She was also on bendroflumethiazide for her blood pressure.

Each product was fine on its own. Together she would have been taking vitamin D from three sources every day, plus calcium, alongside a water tablet that the NHS notes can raise calcium levels with vitamin D. We put the 4,000 IU tablets back on the shelf, checked the multivitamin's vitamin D content, and advised her to keep taking what her GP prescribed and nothing extra, then mention it at her next review. The NHS advice for people prescribed vitamin D is not to take other supplements containing calcium or vitamin D without talking to a doctor first. She had been about to spend money making things worse.

If you already take a calcium and vitamin D tablet on prescription, you almost certainly do not need to buy more.

Free vitamins through Healthy Start

If you qualify for the NHS Healthy Start scheme, you can get free Healthy Start vitamins: tablets containing vitamin D, vitamin C and folic acid while you are pregnant and until your baby's first birthday, and drops containing vitamins A, C and D for children from birth until their fourth birthday. Ask your midwife or health visitor where to collect them locally, and bring your Healthy Start card.

When to see a GP

A daily supplement is about prevention. It is not a treatment for symptoms. See your GP if you have ongoing bone pain, muscle weakness or aches that are not explained, especially if you are in one of the year-round risk groups. Your doctor may arrange a blood test and prescribe a higher, short-term treatment dose if you are deficient, which is very different from the daily maintenance dose. If you think you or a child has taken a large amount of vitamin D by mistake, call 111 for advice. And while there were reports about vitamin D and COVID-19, the NHS says there is not enough evidence to take it solely to prevent or treat COVID-19.

Vitamin D advice at Medway Pharmacy, Gillingham

We are at 465 Canterbury Street, Gillingham, ME7 5LJ, open Monday to Sunday from 7:30am to 10pm, excluding bank holidays. Bring a list of what you already take, including anything prescribed, and we will help you choose a vitamin D product that fits, without doubling up. If you are aged 40 to 74, our free NHS Health Check is also a good time to review your medicines and supplements. Call us on 01634 575805 if you want to check stock first.