How to Read a Vitamin D Label: D2, D3, IU and Micrograms

To read a vitamin D label, find the amount per serve in micrograms (µg or mcg), multiply by 40 to get International Units (IU), then check the ingredient list for the form: cholecalciferol is vitamin D3 and ergocalciferol is vitamin D2. That means 25 µg and 1,000 IU are the same dose written two ways. The percentage figure (% DV, % NRV or % RDI) depends on which country’s reference value the label uses, so compare the micrograms or IU, never the percentage.

This guide explains the unit conversion, why labels differ between countries, D2 versus D3, what the dosage form tells you, how to read drops and sprays, what the reference intakes and upper limits printed in official sources actually mean, and how to compare two products fairly. It is about reading packaging. It does not recommend a dose or make any claim about what vitamin D does for your health.

Where this article links to a product, that link may be an affiliate link and this site may earn a commission at no extra cost to you. See our Affiliate Disclosure.

At a glance

• The one conversion: 1 microgram of vitamin D = 40 IU. So 10 µg = 400 IU, 25 µg = 1,000 IU and 50 µg = 2,000 IU.
• µg and mcg are the same unit. One uses the Greek letter mu, the other is the plain-text version.
• D3 is cholecalciferol, D2 is ergocalciferol. Most D3 is made from lanolin (sheep’s wool); vegan D3 is usually from lichen and says so.
• Ignore the percentage when comparing. A 10 µg product can be “200% NRV” in Europe and “50% DV” in the United States.
• Check the serve: “1,000 IU per serve” may mean one drop, one spray, one tablet or two tablets.

Step 1: convert everything to one unit

Vitamin D is labelled in two units. International Units are a biological measure from before vitamin D could be weighed precisely; micrograms are simply mass. The NIH Office of Dietary Supplements fact sheet sets the relationship at 1 mcg = 40 IU. Pick one unit and convert every bottle you are comparing into it.

Micrograms (µg / mcg)	International Units (IU)	Where you often see it
5 µg	200 IU	Some multivitamins; the EU and UK reference value
10 µg	400 IU	Common single-ingredient and children’s products
15 µg	600 IU	Multivitamins aimed at adults
20 µg	800 IU	Equal to the US Daily Value
25 µg	1,000 IU	A very common capsule strength
50 µg	2,000 IU	Higher-strength single-ingredient products
100 µg	4,000 IU	Equal to the adult upper level used in the US, UK and EU
125 µg	5,000 IU	Above common upper levels; sold in some markets

The trap is that the numbers look nothing alike. A shopper comparing a “1000” on one bottle with a “25” on another can easily think the first is forty times stronger. They are identical.

To go the other way, divide IU by 40. A 400 IU tablet is 10 µg.

Step 2: understand why the percentage changes between countries

Labelling law, not the vitamin, decides which numbers appear and how big they look.

Region	What the label usually shows	Reference value behind the %	What 25 µg looks like
United States	“Supplement Facts” panel, micrograms first, IU often in brackets	Daily Value 20 mcg (800 IU)	125% DV
European Union and United Kingdom	“Food supplement” wording, micrograms and % NRV	Nutrient Reference Value 5 µg	500% NRV
Australia	Listed medicine with an AUST L number; strength commonly given in IU and micrograms	Percentages are less common on supplement labels	Usually just “25 µg (1,000 IU)”

The US Food and Drug Administration updated its labelling rules so that vitamin D is declared in micrograms, with IU allowed alongside, and set the Daily Value at 20 mcg. EU Regulation 1169/2011 sets the vitamin D Nutrient Reference Value at 5 µg, which is why European percentages look dramatic: a 10 µg product is “200% NRV” and simply means 400 IU. In Australia, vitamin D supplements are regulated by the Therapeutic Goods Administration as listed medicines and carry an AUST L number.

The practical lesson: the same brand can carry a different panel in different countries even when the dose is identical. If you buy online from overseas, our guide to buying supplements internationally explains what else changes when a bottle crosses a border.

Step 3: read the form, D2 or D3

The ingredient list names the form, sometimes with its source.

• Vitamin D3 (cholecalciferol) is the form the skin makes in sunlight and the form in animal foods. Most supplement D3 is made from lanolin, a grease from sheep’s wool, so it is not vegan. D3 from lichen is plant-based and labelled as vegan.
• Vitamin D2 (ergocalciferol) is made by exposing yeast or mushrooms to ultraviolet light. It has traditionally been the vegan option and is also used in some prescription products.

According to the NIH fact sheet, the two differ only in their side-chain structure, and in the research it reviews D3 raises blood levels of 25-hydroxyvitamin D (the marker doctors usually test) more, and keeps them up for longer, than D2. That is a statement about a laboratory measurement, not about any health outcome. It explains why most shelf products are D3.

Label wording	Form	Usual source	Vegan?
Cholecalciferol (from lanolin)	D3	Sheep’s wool grease	No (vegetarian for some people)
Cholecalciferol (from lichen)	D3	Lichen	Yes, if the capsule shell is also plant-based
Ergocalciferol	D2	UV-treated yeast or mushrooms	Usually yes
“Vitamin D” with no form named	Check the panel	Unknown	Ask the maker or pharmacist

Step 4: check the dosage form and the serve

Vitamin D is fat-soluble, and the format is one of the more useful things the label tells you.

Softgel capsules

The vitamin is dissolved in a carrier oil such as olive, sunflower, MCT (coconut-derived) or fish oil, and the label names it. Shells are usually gelatin from cattle or fish; plant-based shells say so. If you avoid fish or bovine products, this line matters more than the dose.

Tablets and chewables

The vitamin sits on a powder base with fillers and binders, so the “other ingredients” list is longer. Tablets are often the cheapest per dose. Chewables and gummies add sweeteners and flavours, and are easy to over-eat, so keep them out of children’s reach.

Drops and sprays

These cause the most confusion. A label may state the amount per drop, per spray, per millilitre or per “serve” of several drops. A dropper can hold many drops, so “1,000 IU per serve” might be one drop or a full dropperful. Read the small print for the amount per single drop or spray before you compare.

Combination products

Vitamin D is often paired with calcium, vitamin K2 or magnesium. Each ingredient is a separate label question. A D3 and K2 product should give the K2 form (MK-4 or MK-7) and its amount; our guide to vitamin D3 and K2 together covers what the research on that pairing tested. Calcium has its own form choice, explained in calcium citrate vs carbonate.

Step 5: put the strength in context

Strengths on sale range from 5 µg (200 IU) in some multivitamins to 125 µg (5,000 IU) and above in single-ingredient products. Official reference values give the number on the bottle some context. They are not targets, and they differ between countries.

Source	Adult reference intake	Adult upper level
US (NIH Office of Dietary Supplements)	RDA 15 µg (600 IU) to age 70; 20 µg (800 IU) over 70	100 µg (4,000 IU) a day
UK (NHS)	10 µg (400 IU) a day suggested, especially in autumn and winter	NHS advises not taking more than 100 µg (4,000 IU) a day
Australia and New Zealand (NHMRC Nutrient Reference Values)	Adequate Intake 5 µg (19-50 years), 10 µg (51-70), 15 µg (over 70)	80 µg (3,200 IU) a day

The upper level is the highest daily intake considered unlikely to cause harm in the general population. It is not a goal, and some people are advised by their doctor to take more for a set period after a blood test. That is a clinical decision. If a product’s strength is at or above the upper level where you live, talk to your doctor or pharmacist before using it.

Remember to add up every source. A multivitamin, a calcium-plus-D tablet and a separate vitamin D capsule can stack up quickly. Our multivitamins after 50 guide shows how to read the vitamin D line on a multi.

Step 6: read the rest of the panel

• Serving size: usually one capsule, but some products split the stated dose across two.
• Servings per container: the count on the front divided by the serving size.
• Other ingredients: carrier oil, shell, fillers such as microcrystalline cellulose, and flow agents such as magnesium stearate or silica.
• Allergen statement: fish oil carriers and fish gelatin shells must be declared in most markets.
• Batch and expiry: worth checking on large multipacks that will take a year or more to finish.
• Regulatory marks: AUST L in Australia, a Supplement Facts panel in the US, “food supplement” wording in the EU and UK. Independent testing seals are a separate thing; see what USP, NSF and Informed Sport mean.

Step 7: compare cost fairly

Vitamin D is one of the cheaper supplements per dose, so price per microgram rarely decides the purchase on its own. It matters most when comparing premium options such as lichen D3, liposomal products or combination blends, which can cost several times more per microgram of vitamin D.

Worked example: Bottle A has 60 softgels of 25 µg. Bottle B has 120 tablets of 1,000 IU, one tablet per serve. Convert B: 1,000 ÷ 40 = 25 µg. Both give 25 µg per serve, so compare price per serve: divide each price by its number of serves. Bottle B has twice as many serves, so it is better value unless its price is more than double Bottle A’s. Then check the form, oil and shell before deciding.

Vitamin D label checklist

1. Find the amount per serve and convert it: micrograms × 40 = IU, or IU ÷ 40 = micrograms.
2. Confirm the serve: one capsule, two tablets, one drop or a dropperful.
3. Read the form in the ingredient list: cholecalciferol (D3) or ergocalciferol (D2), and the source if it matters to you.
4. Check the carrier oil, shell material and allergen statement.
5. For combination products, read each ingredient’s amount separately.
6. Add up vitamin D from every product you take, including multivitamins.
7. Compare the total with your country’s upper level, and ignore the percentage when comparing brands.
8. Check expiry and the regulatory mark for the country of sale.
9. If you take medicines, have a medical condition, are pregnant or are buying for a child, talk to your doctor or pharmacist first.

Common mistakes

• Comparing IU with micrograms directly. 1,000 IU is not more than 25 µg; they are equal.
• Comparing percentages across countries. % NRV, % DV and other percentages use different reference values.
• Misreading drops. Taking a dropperful when the label dose is one drop can multiply the intake many times over.
• Forgetting the multivitamin. Doubling up from several products is the usual way people end up above the upper level without noticing.
• Assuming “vegan” from the word “vitamin D”. Most D3 comes from lanolin, and many shells are gelatin.
• Treating a higher number as a better product. Strength is not quality; the right amount is something to discuss with a health professional who knows your blood results.

For the bigger picture on testing and sunlight in a sunny climate, see vitamin D in Australia: sunlight and testing. For general label skills that apply to every bottle, start with how to read a supplement label, and for every other vitamin and mineral, our supplements evidence and label guide is the place to begin.

Sources this guide draws on: NIH Office of Dietary Supplements, Vitamin D Fact Sheet for Health Professionals; US Food and Drug Administration, Dietary Supplement Labeling Guide and Daily Value rules; EU Regulation 1169/2011, Annex XIII; NHS guidance on vitamin D; NHMRC Nutrient Reference Values for Australia and New Zealand; Therapeutic Goods Administration guidance on listed medicines.

Frequently asked questions

Is 1,000 IU the same as 25 mcg?

Yes. One microgram of vitamin D equals 40 IU, so 25 mcg × 40 = 1,000 IU. Labels that show one or the other are describing the same amount.

Is D3 or D2 better on a label?

The NIH fact sheet reports that D3 raises and maintains blood 25-hydroxyvitamin D levels more than D2 in the studies it reviews, which is why most products are D3. D2 and lichen-based D3 are the usual vegan choices. Which suits you is worth discussing with your doctor or pharmacist, especially if you have had a blood test.

What does “% NRV” mean on a vitamin D label?

It is the percentage of the EU and UK Nutrient Reference Value, which is 5 µg for vitamin D. That small reference figure is why European labels show large percentages, such as 200% for a 10 µg product.

Why does my vitamin D bottle have an AUST L number?

In Australia, vitamin D supplements are listed medicines regulated by the Therapeutic Goods Administration, and the AUST L number shows the product is on the Australian Register of Therapeutic Goods. It tells you which rules apply, not that the product has been tested for effectiveness.

How do I read the dose on vitamin D drops?

Look for the amount per single drop, not just per serve. Some products give 1,000 IU in one drop, others in several drops or a full dropper. Measure exactly as the label says.

Can you take too much vitamin D?

Yes. Official bodies set upper levels, such as 100 µg (4,000 IU) a day for adults in the US and UK, and 80 µg in Australia and New Zealand. Add up every product you take, and talk to your doctor or pharmacist before using a high-strength product.

Once you can convert units and spot the form, any vitamin D label takes about a minute to read. Compare micrograms, check the serve and the form, total every source, and leave the question of how much you need to a conversation with your doctor or pharmacist.

This guide is general education about reading labels. It is not medical advice and does not recommend a dose. Talk to your doctor or pharmacist before starting a supplement, particularly if you take medicines or have a health condition.