Medically reviewed by Hajra Dhanchora, MPharm (GPhC 2216990) · Last reviewed August 2026
A balanced diet gives most people the vitamins and minerals they need. But a few supplements are genuinely worthwhile — particularly at certain times of year or life — and it helps to know which ones, how much, and when to take them.
Vitamin D: the one almost everyone in the UK should consider
Vitamin D helps your body absorb calcium and keeps bones, teeth and muscles healthy. Your skin makes it from summer sunlight, but between October and March the sun in the UK isn't strong enough — so it's hard to make enough from sunlight alone.
How much vitamin D per day?
Public health advice is that adults and children over one should consider a daily 10 microgram (400 IU) supplement during autumn and winter. Some people should take it all year round: those who are rarely outdoors, usually cover their skin, or have darker skin, as they may not make enough even in summer. Babies and young children have their own recommendations — ask our pharmacist.
Can you take too much vitamin D?
Yes. Because vitamin D is fat-soluble, it builds up in the body, so more is not better. For most adults, no more than 100 micrograms (4,000 IU) should be taken per day unless a doctor has advised it — too much over time can raise blood calcium and harm the bones and kidneys. Stick to the recommended amount unless you've been told otherwise.
Is vitamin D3 the same as vitamin D?
"Vitamin D" on a label usually means D3 (cholecalciferol) or D2 (ergocalciferol). Both work, but D3 is generally more effective at raising and maintaining your levels, which is why most supplements use it. As it's fat-soluble, take it with a meal for better absorption.
Which foods contain vitamin D?
Good sources include oily fish (salmon, sardines, mackerel), egg yolks, red meat and fortified foods such as some breakfast cereals and fat spreads. Diet alone rarely provides enough over winter, which is why a supplement is recommended.
Folic acid if you're planning a pregnancy
If you're trying for a baby or in the early weeks of pregnancy, folic acid helps your baby's development and reduces the risk of neural tube defects. The usual advice is 400 micrograms a day from before conception until 12 weeks of pregnancy — but some women need a higher dose, so your midwife or GP can advise on what's right for you.
Vitamin B12 and iron: only if you need them
Vitamin B12 is found mainly in animal products, so if you follow a vegan or strict vegetarian diet you may need a supplement or fortified foods. Iron is important, but you shouldn't take it routinely "just in case" — too much can cause side effects, and low iron should be confirmed (usually with a blood test) and the cause looked into. If you often feel very tired, speak to your GP rather than self-treating with iron.
Omega-3 and other supplements
Omega-3 (from oily fish or fish-oil supplements) supports heart health, and many people who don't eat much oily fish choose to top up. Beyond the specific cases above, most healthy adults eating a varied diet won't get extra benefit from a general multivitamin.
Do you need a multivitamin?
Many multivitamins offer more than most healthy adults actually need, and a few contain high levels of nutrients that are best not taken in excess. Rather than a random, unplanned approach, it's usually better to choose the supplement that is most appropriate for you — vitamin D over winter, folic acid around pregnancy, B12 on a vegan diet — and get the rest from food.
How to choose and take supplements safely
- Check for interactions. Some supplements affect prescription medicines — for example, high-dose supplements and blood thinners. Always tell our pharmacist what you take.
- Take fat-soluble vitamins (A, D, E, K) with food. They absorb better with a meal.
- Don't double up. If you take a multivitamin and a separate single vitamin, check you're not exceeding safe amounts.
- More isn't better. Stick to recommended amounts unless a clinician advises otherwise.
Browse our Vitamins & Supplements range, and if you're unsure whether a supplement is worth taking — especially alongside other medicines — our pharmacist can help.
Common questions
What does vitamin D do? It helps regulate calcium and phosphate, keeping bones, teeth and muscles healthy.
When should I take vitamin D? With a meal, at whatever time of day suits you — consistency matters more than timing.
Can you overdose on vitamins? You can take harmful amounts of some, particularly fat-soluble vitamins like A and D, which build up in the body. Water-soluble ones (like vitamin C) are less of a concern, but very high doses can still cause side effects.
Want tailored advice? Our GPhC-registered pharmacists are happy to help — visit Talk to a Pharmacist.
This article is general information and is not a substitute for advice from a healthcare professional. If you take other medicines or have a health condition, check with your pharmacist or GP before starting a supplement.