How to Pick the Right Vitamins for Your Body

You’ve likely stood in the vitamins and supplements aisle, feeling overwhelmed by the endless options and combinations. But randomly selecting one to just feel healthier isn’t the answer.

In this guide, we'll help you work out which vitamins you actually need, and when supplements are worth your money. We’ll also explain those confusing vitamin measurements in simple terms, all so you can shop for vitamins with confidence.

Three key takeaways

  1. Most people only need vitamin D (and B12 if you have a plant-based diet). The majority of vitamins come from a balanced diet, with vitamin D coming from exposure to sunlight.
  2. Taking some supplements can be harmful without a deficiency. Iron, vitamin A, and vitamin E can cause serious issues if taken unnecessarily. Always check with your GP first.
  3. Understanding units prevents mistakes. Knowing that 400 IU = 10 mcg of vitamin D helps you compare products and avoid overdosing or underdosing.

Woman taking vitamin with a glass of water.

Are vitamins worth taking every day?

Yes, vitamins (if you need them) are worth taking every day, but only if you stick with it.  Their benefits range from boosting your immune system to increasing your energy levels, but taking vitamins sporadically won't deliver any meaningful benefits.

You wouldn’t expect a skincare product to start working after the first use, and vitamins aren’t any different. It’s only with daily, consistent use that you’ll notice any positive changes.

“If you do take vitamins, it’s important to remember to take them daily as your body either can't store them or uses them up quickly. Whether they're worth taking depends on your individual needs: someone with a balanced diet might need minimal supplementation, while those with dietary restrictions could genuinely benefit from a daily supplement routine.”

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Ian Budd, Prescribing Pharmacist at Chemist4U

Vitamin units explained 

If you've ever squinted at a supplement label trying to work out whether 400 IU is the same as 10 mcg (it is, for vitamin D), you're not alone.

The vitamin industry seems determined to make things as confusing as possible, with different vitamins measured in different units—and sometimes, the same vitamin’s units can be listed differently across brands.

We're keeping it simple. Take a look below at some of the most common unit breakdowns and what vitamins use each measurement.

UnitWhat it stands forWhat it measuresCommonly used for
IUInternational UnitsBiological activity/potencyVitamins A, D, E
mcg (μg)MicrogramsWeight (1/1000 of a milligram)B12, D, K, folate
mgMilligramsWeight (1/1000 of a gram)Vitamin C, B vitamins, E
mcg RAERetinol Activity EquivalentsVitamin A activityVitamin A only
mcg DFEDietary Folate EquivalentsFolate activityFolate/folic acid
NENiacin EquivalentsNiacin activityVitamin B3

What vitamins and minerals should you take? 

Not all vitamins are created equal, and most importantly, not everyone needs every supplement. Some are essential for most people (like vitamin D in the UK during autumn and winter), while others can be harmful if taken without a confirmed deficiency.

Here's what you need to know about the key vitamins and minerals.

Vitamin A 

How it helpsSupports vision, immune function, and skin health.
Recommended dose600-900 mcg RAE daily.
Where it's foundOrange/yellow veg (carrots, sweet potatoes), liver, dairy, dark leafy greens.
Should you supplement?Rarely needed - speak to GP first. Easy to get from diet. Too much can be toxic.

B vitamins and folic acid 

How it helpsEnergy production, nerve function, red blood cell formation. Folic acid crucial for pregnancy.
Recommended doseB12: 1.1-1.3 mcg. Folate: 400-600 mcg DFE. Others vary.
Where it's foundWhole grains, meat, eggs, legumes, leafy greens.
Should you supplement?B12: Yes, if vegan/vegetarian. Folic acid: Essential if pregnant/trying. Others: Usually unnecessary unless diagnosed with a deficiency.

Vitamin C 

How it helpsImmune support, collagen production, antioxidant protection.
Recommended dose75-125 mg daily.
Where it's foundCitrus fruits, peppers, strawberries, broccoli, tomatoes.
Should you supplement?Optional - consider during winter or if diet lacks fruit/veg. Excess is harmless but wasteful.

Vitamin D 

How it helpsBone health, immune function, mood regulation.
Recommended dose10 mcg (400 IU) daily.
Where it's foundSunlight, oily fish, fortified foods, egg yolks.
Should you supplement?Yes, for all UK residents during autumn and winter (Oct-March). Safe and recommended by NHS.

Vitamin E 

How it helpsAntioxidant, skin health, immune support.
Recommended dose15 mg daily.
Where it's foundNuts, seeds, vegetable oils, avocados.
Should you supplement?Rarely needed - abundant in diet. High doses can interfere with blood clotting.

Vitamin K 

How it helpsBlood clotting, bone health.
Recommended dose75-120 mcg daily (depending on body weight).
Where it's foundLeafy greens, broccoli, Brussels sprouts.
Should you supplement?No, unless prescribed - check with GP if on blood thinners. Deficiency is rare.

Calcium 

How it helpsBone and teeth health, muscle function, nerve signalling.
Recommended dose700-1000 mg daily.
Where it's foundDairy, fortified plant milks, leafy greens, tinned fish.
Should you supplement?Maybe, if dairy-free or at risk of osteoporosis. Best absorbed with vitamin D.

Iodine 

How it helpsThyroid function, metabolism regulation.
Recommended dose140 mcg daily.
Where it's foundDairy, seafood, iodised salt, seaweed.
Should you supplement?Check with GP - especially if pregnant or vegan. Too much affects thyroid.

Iron 

How it helpsOxygen support, energy production, immune function.
Recommended dose8-27 mg daily (varies by age, gender, pregnancy).
Where it's foundRed meat, beans, fortified cereals, spinach.
Should you supplement?Only if deficient - requires blood test first. Unnecessary iron is harmful and can damage organs.

Magnesium 

How it helpsMuscle/nerve function, energy production, sleep quality.
Recommended dose270-300 mg daily.
Where it's foundNuts, seeds, whole grains, leafy greens, dark chocolate.
Should you supplement?Consider if stressed/poor sleep - generally safe but can cause digestive issues.

Zinc

How it helpsImmune function, wound healing.
Recommended dose7-9.5 mg daily.
Where it's foundMeat, shellfish, legumes, seeds, nuts.
Should you supplement?Short-term only - for colds/immunity. Long-term use can interfere with copper absorption.

Can you take too many vitamins?

Yes, and it's easier than you'd think. While your body flushes out excess water-soluble vitamins (like vitamin C), fat-soluble vitamins (A, D, E, K) build up in your body and can reach toxic levels.

Dangerous vitamins you can overdose on include:

  • Vitamin A: can cause liver damage and brittle bones.
  • Iron: can cause organ damage without warning signs.
  • Vitamin D: can lead to kidney stones and heart problems.
  • Zinc: weakens immunity when taken in excess.

When you combine certain vitamins, they can also block each other's absorption or interfere with medications:

  • iron + calcium = poor iron absorption (take at different times)
  • zinc + copper = zinc depletes copper, causing anaemia
  • vitamin E + blood thinners = increased bleeding risk
  • multiple supplements = accidental overdose from overlapping ingredients

Taking more doesn’t mean you will reap greater benefits. Always stick to the recommended doses, check for overlapping ingredients across all of your supplements, and always tell your GP what you're taking.

7 tips on taking vitamins 

  1. Take vitamins at the same time daily to build a routine. Consistency matters!
  2. Fat-soluble vitamins (A, D, E, K) need food with fat for absorption, while iron works best on an empty stomach.
  3. Take B vitamins in the morning as they boost energy and magnesium at night to help you relax.
  4. Split calcium doses throughout the day since your body can only absorb 500 mg at once.
  5. Store vitamins in a cool, dry place away from sunlight, not in the bathroom cabinet, as humidity reduces their effectiveness.
  6. Check expiry dates regularly as vitamins lose potency over time.
  7. Use a pill organiser if you're forgetful. Double-dosing on certain vitamins can be harmful.

FAQs

What vitamins are recommended when pregnant? 

Take folic acid (400 mcg) before getting pregnant and for the first 12 weeks, plus vitamin D (10 mcg) throughout pregnancy. Most pregnancy vitamins have everything you need, but you should not take extra vitamin A supplements as it can harm your baby.

Which vitamins are best for fatigue? 

Tiredness usually means you're low in iron, B12, or vitamin D. Get a blood test to check which one you need rather than guessing. If your fatigue doesn't improve with supplements, see your GP as something else might be causing it.

What vitamins should I take daily as a woman? 

Most women just need vitamin D in autumn and winter. Take folic acid if you’re trying to get pregnant, consider iron if your periods are heavy, and add B12 if you don't eat meat or dairy.

What vitamins should I take daily as a man? 

Men usually only need vitamin D in autumn and winter, plus B12 if vegetarian or vegan. Don't take iron unless a blood test shows you need it.

What vitamins should I take on Mounjaro?

As you’ll be eating less with weight-loss injections, you could be missing out on key nutrients. Take vitamin D, B12, and a basic multivitamin, but avoid high doses of iron or magnesium as these can upset your stomach.

Sources

  1. Vitamin D. NHS. Accessed 15th October 2025.
  2. Vitamins and Minerals. British Nutrition Foundation. Accessed 15th October 2025.
  3. B Vitamins. NHS. Accessed 15th October 2025.
  4. Vitamin A. NHS. Accessed 15th October 2025.
  5. Vitamin C: Can It Help Prevent Colds? Mayo Clinic. Accessed 15th October 2025.
  6. Vitamin E. Mayo Clinic. Accessed 15th October 2025.
  7. Vitamin K. NHS. Accessed 15th October 2025.
  8. Calcium. NHS. Accessed 15th October 2025.
  9. Iodine. NHS. Accessed 15th October 2025.
  10. How Much Iron Do You Need Per Day? Healthline. Accessed 15th October 2025.
  11. Other Vitamins and Minerals. NHS. Accessed 15th October 2025.
  12. Magnesium. StatPearls. NCBI Bookshelf. Accessed 15th October 2025.
  13. The Role of Zinc in Human Health. 2016. ScienceDirect. Accessed 15th October 2025.
  14. Vitamin D Toxicity: What If You Get Too Much? Mayo Clinic. Accessed 15th October 2025.
  15. Vitamin Toxicity. StatPearls. NCBI Bookshelf. Accessed 15th October 2025.
  16. Drug-Induced Vitamin B6 Deficiency. 2004. PubMed. Accessed 15th October 2025.
  17. Interactions Between Iron and Vitamin A, Riboflavin, Copper and Zinc. 2001. PubMed. Accessed 15th October 2025.
  18. Calcium-Iron Interactions. 1996. PubMed. Accessed 15th October 2025.
  19. Vitamin Toxicity: Symptoms and Diagnosis. Verywell Health. Accessed 15th October 2025.
Ian Budd - Prescribing Pharmacist
Ian Budd , Prescribing Pharmacist on 16 October 2025
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