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What Does ug Mean In Vitamin D

What Does ug Mean In Vitamin D? (FREE µg to IU Calculator)

by Eric Sales De Andrade, May 25th 2021

Reading Time: 6 minutes

Have you looked at a Vitamin D supplement and wondered what does ug mean in Vitamin D?

Or the “IU” written in big and bold on the front of the packaging?

Unfortunately, health supplement companies don’t do a great job educating you to understand how to choose the right vitamin.

Knowing the basics of how Vitamin D strength is reported will help you choose the correct one.

If you’re looking to buy or take Vitamin D supplements, this article is for you.

I’ll talk about what ug and IU mean, how to convert back and forth between them and how to check your Vitamin D levels.

I’ll also share tips on how much Vitamin D to take based on your levels to correct them and return to normal.

As someone who’s spent over 5 years learning about health supplements, I’ll also share some secret tips on buying health supplements.

What Does ug Mean In Vitamin D?

ug is actually “μg” which is the Greek Symbol for micro “μ”, followed by “g” for gram. 1000 microgram makes up 1 milligram (“mg”).

μg is the amount of active Vitamin D used in health supplements, not including binders and fillers.

It’s also often expressed as IU (International Unit) and the conversion is 1 μg = 40 IU.

FREE Vitamin D µg to IU Calculator

Easily calculate Vitamin D from μg (Microgram) to IU (International Unit), back and forth.

(Enter a value in one field and the other one will update automatically)

1 µg = 40 IU

Is ug The Same As IU?

Not really, but they are both a measure of active Vitamin D concentration.

As said above, μg is the Greek symbol for micro “μ” followed by the symbol for gram “g”.

One microgram equals one-thousandth of a milligram and one milligram equals one-thousandth of a gram.

In pharmacology, the International Unit (or IU) is the unit of measurement of the amount of the substance.

It tells you how much active Vitamin D is present in the capsule based on its biological activity.

The conversion factor is 1 μg = 40 IU.

For example

  • 10 µg = 400 IU
  • 25 µg = 1000 IU
  • 50 µg = 2000 IU

And so on.

Hopefully, the answer to what does ug mean in Vitamin D starts to make complete sense now.

It’s just a measure of the amount of Vitamin D present in a capsule or supplement.


How Much Vitamin D Should I Take?

This is a good question and one we get asked a lot.

Unfortunately, like anything else in the health space, there is no one size fits all.

If anyone tells you how much to take off the bat, they probably don’t know better or don’t have your best interest at heart.

Like a medicinal drug, there are guidelines and assumptions.

But to get the best out of it, you need to find what your body needs, via a blood test.

A guideline is if you get regular sunshine you don’t need a strong dose and 25–50 μg Vitamin D per day should suffice.

You can learn more about how is Vitamin D made in our other article.

But, if you’re having deficiency symptoms like insomnia, bone pain, dizziness, nausea, chronic fatigue, the situation is more urgent.

In this case, you’ll need to do a blood test urgently.

Depending on the levels, your GP will recommend a strong Vitamin D loading dose followed by maintenance supplements.

It’s also recommended to take Vitamin D Cofactors supplements to reduce any possibility of Calcium toxicity caused by strong Vitamin D supplements.

If you have a major deficiency, the priority here is to correct it based on the Vitamin D Levels Chart UK.

Dr Chris Steele (MBE), resident doctor on This Morning’s Daytime Magazine show says

Vitamin D is made in your skin and in the action of sunshine. We are all low on vitamin D, and we should be taking vitamin D.

The NHS Website also says

If you choose to take vitamin D supplements, 10 micrograms a day will be enough for most people.

Don’t take more than 100 micrograms of vitamin D a day as it could be harmful.

This applies to adults, including pregnant and breastfeeding women and the elderly, and children aged 11 to 17 years.

Is 25 ug Vitamin D Enough?

For most people who get enough sunshine and eat plenty of Vitamin D rich food, 25 μg (or 1000 IU) should be enough.

But, if you don’t get enough sunshine or during winter, you need stronger Vitamin D doses (like 50 μg +).

If you’re deficient it’s important to do a blood test and take stronger doses to correct your levels.

Vitamin D tests

Testing Your Vitamin D Levels

We’ve spoken about your needs. How everyone is different and why a one size fits all supplement can’t really treat a deficiency.

If you don’t have deficiency symptoms it may be OK to take generic Vitamin D of 1000 IU or 2000 IU/day strength.

But if you have symptoms it’s important you address them by means of a blood test. Otherwise, the long term health consequences could be devastating.

You should be able to make an appointment at your local GP for a blood test.

But, at the time of this article, the world is going through an unfortunate crisis of the Covid 19 Pandemic.

This has severely restricted the health system’s ability to allocate resources for lower-priority Vitamin D testing.

In the event that you’re unable to get an appointment or it’s too far off, you can always take a Vitamin D Home Test.

This is a relatively easy and inexpensive option.

It involves buying a Vitamin D Test Kit, taking a blood sample and posting it to the company via a pre-paid envelope.

I cover 6 tips for choosing the best Vitamin D Test Kit UK in our other article.

Your results are available within 2–5 days securely via an App or Dashboard.


Understanding Your Vitamin D Results

So once you’ve checked your Vitamin D levels, what’s your next step?

You need to understand your results.

Sure, you can rely on your GP. But bear in mind that GPs are not specially trained to correct Vitamin deficiencies.

It’s important you pay attention to the results too and work with your GP to fix your low Vitamin D levels.

The Vitamin D Levels Chart UK contains most of the information you need to know to fix low Vitamin D.

Vitamin D levels are measured in (nmol / L) or (ng / mL) and described as

  • Deficient (< 30 nmol/L)
  • Insufficient (30–50 nmol/L)
  • Adequate (50–75 nmol/L)
  • Optimal (75–125 nmol/L)
  • Too High (> 125 nmol/L)

Based on your Vitamin D levels, you can take corrective action to get back into tip-top health.

Vitamin D Capsules coming out of a bottle

Buying Correct Vitamin D Supplements

With well over a thousand Vitamin D brands on the market, how do you choose the best one?

Is there even such a thing as the best one or they all seem the same?

Most people cannot tell the difference because frankly there isn’t too much.

Yet, there are a few things to keep in mind when buying health supplements.

This will help you separate the cream of the crop.

6 Tips For Buying Health Supplements

Here are 6 tips for buying the best Vitamin D supplements. Look for these 6 key things

  • Whole-food and sustainable (preferably vegan) ingredients.
  • Highly absorbed formula i.e. has fat for fat-soluble vitamins, with complementary ingredients.
  • Correct dosage strength — not too weak that you don’t see benefits, not too strong that it makes you sick.
  • Mode of consumption — capsules, tablets, soft gels, spray, see what works for you best.
  • Allergens
  • Certifications — Vegan, Organic, Vegetarian


I dive deep into each of the above points in my article on 6 Honest Tips for Buying Quality Vitamins and Supplements.


I hope this article helped you understand what does ug mean in Vitamin D, the difference between μg and IU and how to convert one to the other.

1 µg = 40 IU so keep this in mind next time you buy Vitamin supplements.

You also learnt how to check your Vitamin D levels and correct a deficiency should you have one.

Since Vitamin deficiencies are not as serious as other major conditions they are often deprioritised.

But their consequences can be painful and uncomfortable.

So it’s important you stay proactive, take control and fix them.

Your next step,

Join our Vitamin D Fan Club — a private Facebook group.

Here you’ll connect with fellow health lovers and learn all things Vitamin D, all things natural supplements.

FREE Vitamin Cheat Sheet

Learn How Much Of Each Vitamin You Need Per Day With Our FREE Cheat Sheet 

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