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
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.
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.
Understanding units prevents mistakes. Knowing that 400 IU = 10 mcg of vitamin D helps you compare products and avoid overdosing or underdosing.
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.”
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.
Unit
What it stands for
What it measures
Commonly used for
IU
International Units
Biological activity/potency
Vitamins A, D, E
mcg (μg)
Micrograms
Weight (1/1000 of a milligram)
B12, D, K, folate
mg
Milligrams
Weight (1/1000 of a gram)
Vitamin C, B vitamins, E
mcg RAE
Retinol Activity Equivalents
Vitamin A activity
Vitamin A only
mcg DFE
Dietary Folate Equivalents
Folate activity
Folate/folic acid
NE
Niacin Equivalents
Niacin activity
Vitamin 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 helps
Supports vision, immune function, and skin health.
Recommended dose
600-900 mcg RAE daily.
Where it's found
Orange/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 helps
Energy production, nerve function, red blood cell formation. Folic acid crucial for pregnancy.
Recommended dose
B12: 1.1-1.3 mcg. Folate: 400-600 mcg DFE. Others vary.
Where it's found
Whole 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.
Maybe, if dairy-free or at risk of osteoporosis. Best absorbed with vitamin D.
Iodine
How it helps
Thyroid function, metabolism regulation.
Recommended dose
140 mcg daily.
Where it's found
Dairy, seafood, iodised salt, seaweed.
Should you supplement?
Check with GP - especially if pregnant or vegan. Too much affects thyroid.
Iron
How it helps
Oxygen support, energy production, immune function.
Recommended dose
8-27 mg daily (varies by age, gender, pregnancy).
Where it's found
Red 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 helps
Muscle/nerve function, energy production, sleep quality.
Recommended dose
270-300 mg daily.
Where it's found
Nuts, 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 helps
Immune function, wound healing.
Recommended dose
7-9.5 mg daily.
Where it's found
Meat, 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)
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
Take vitamins at the same time daily to build a routine. Consistency matters!
Fat-soluble vitamins (A, D, E, K) need food with fat for absorption, while iron works best on an empty stomach.
Take B vitamins in the morning as they boost energy and magnesium at night to help you relax.
Split calcium doses throughout the day since your body can only absorb 500 mg at once.
Store vitamins in a cool, dry place away from sunlight, not in the bathroom cabinet, as humidity reduces their effectiveness.
Check expiry dates regularly as vitamins lose potency over time.
Use a pill organiser if you're forgetful. Double-dosing on certain vitamins can be harmful.
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.
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