Our expert has put together all the information you need on choosing and taking supplements. Find out which ones are worth your money, how to take them for best effectiveness, and how to avoid problems such as taking too much.


Check out our Vitamins and Minerals Information Hub to learn more about key nutrients – from whether you’re getting enough vitamin D to the top 10 healthiest sources of vitamin C, plus vital minerals you need in your diet.

Which product should I choose?

  • Be cautious where you source your supplements – buy from a reputable company.
  • Look for a manufacturer that adheres to Good Manufacturing Practice (GMP) standards – this is not mandatory for supplement producers but is an indication that the product has been produced to the highest of standards.
  • Do your homework – does the product deliver an effective dose (you can check recommended daily intake – also known as NRV – together with the safe upper level guidance for most nutrients here).
  • There are no guidance amounts for supplements like omega-3 or herbal extracts; for omega-3, choose a supplement that supplies the same daily amount of EPA and DHA as one or two portions of oily fish per week (450mg EPA and DHA); for herbals look for research into their efficacy, and the dose used on study subjects.
  • Check the formulation of the nutrient is the most easily absorbed and the best choice for you. For example, nutrients in powder form may be better if you can’t swallow pills and liquids are good if you need a higher dose, but want it in a smaller amount.

How to take supplements safely

  • A ‘natural’ product doesn’t equate to safe – the safety of a product depends on how it was prepared, how it works in the body, how much you take and its suitability for your personal circumstances.
  • Read the product information – including ingredients, drug interactions and percent of nutrient reference value (NRV%).
  • Check the product carries a batch number and expiry date.
  • Choose a formulation suitable for your age and gender.
  • Take supplements as directed on the label.
  • Keep away from children and animals.
  • Track your supplement use so you can identify when you may be doubling up.

How best to take your supplement

When to take:

  • Take fat-soluble vitamins (A, D, E and K) with a meal containing some fat such as olive oil or avocado – this improves absorption.
  • Take water-soluble vitamins (vitamins C and the B group) on an empty stomach with a glass of water.
  • Take B vitamins in the morning for their energising effect.
  • Take pre-natal supplements (including folic acid) with your evening meal.
  • Take magnesium or calcium in the evening as they may aid sleep.

What to take it with:

  • Calcium is optimised by vitamins D and K so take them together.
  • Take your iron supplement away from food but with vitamin C-rich orange juice to aid absorption.

What to avoid taking at the same time:

More like this
  • Vitamin C hinders the absorption of vitamin B12 – take at least two hours apart.
  • Avoid calcium-rich foods or supplements with iron - if you take both minerals, take iron in the morning and calcium at night.
  • Minerals like magnesium, zinc and calcium should be taken with food but at different meals to optimise absorption.
  • Alternate day supplementation may be more effective for some nutrients, like iron.
  • Watch your caffeine intake – it may reduce absorption of certain vitamins and because it’s a diuretic it may cause you to excrete water-soluble vitamins.

When might I be at risk of overdosing?

White woman poised to take a golden-coloured capsule

Those seeking ‘optimal’ health or looking to prevent or manage certain conditions often believe that taking vitamins and minerals in larger amounts may be more effective. However, there is established evidence that when certain nutrients (including vitamins A and D as well as the mineral selenium) are consumed in excessive amounts, toxic levels may occur. It can sometimes be easier to reach this level than you might realise. For example, for vitamin A, toxic effects can occur for infants and pregnant women at only three times the daily recommended amount (reference intake).

You should be careful, then, with supplements – especially as high dose products are widely available, or because taking multiple products is fairly common practice. And remember that the supplements industry is unregulated, with some establishments offering products without proper assessment or informed consent.

Which supplements should I be careful with?

Supplement use for these high-risk groups should always be discussed with a medical professional:

  • the young,
  • the elderly,
  • pregnant and breast-feeding women,
  • patients who are immune-compromised,
  • those due to undergo surgery,
  • anyone on prescribed medication.

This is because certain groups may need to avoid some products. For example, if you are pregnant, you should avoid fish liver oil capsules because the vitamin A content may be harmful to your baby. Those with high blood pressure may be advised to avoid fizzy vitamin supplements because some of these products contain as much as a gram of salt per tablet.

Similarly, iron supplements may be harmful for people who don’t need them. Smokers and former smokers may need to be cautious of large amounts of beta-carotene and vitamin A because studies suggest an increased risk of lung cancer. Also, those on prescribed medication to reduce blood clotting, such as warfarin, should refer to their GP before supplementing with vitamin K, this is because this vitamin reduces the effectiveness of the medication. Other supplements that may be contra-indicated with blood thinners include Ginkgo biloba, vitamin E and high doses of omega-3 fish oils.

Further reading…

Vitamins: what do I need?
Vital minerals: what do I need?
Vitamin health hacks


All health content on bbcgoodfood.com is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other health care professional. If you have any concerns about your general health, you should contact your local health care provider. See our website terms and conditions for more information.

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