Q. Most nutrients seem to be measured in mg but some are shown as mcg or I.U. How do I convert these measurements into mg?
A. To convert micrograms (mcg) to milligrams (mg), divide by 1,000–or move the decimal point 3 positions to the left. 1000 mcg = 1.000 mg. But generally, you won’t need to convert between these two. We use micrograms for nutrients that occur in very small amounts (folate, vitamin B12, vitamin D, and vitamin K, for example). Instead of writing that a food contains 0.125 mg of vitamin K, it’s less confusing to write that it contains 125 mcg. You generally wouldn’t find milligram amounts of vitamin K in foods or supplements.
Converting International Units (I.U.) isn’t so simple–because it’s a different conversion for each nutrient. The I.U. is an arbitrary amount based on the amount of a given nutrient needed to produce a biological effect. Here are the conversions for the most common nutrients.
| Nutrient | Amount in 1 I.U. |
|---|---|
| Vitamin A | 0.3 mcg |
| Beta-carotene | 3.6 mcg |
| Vitamin D | 0.025 mcg |
| Vitamin E | 0.67 mg |
_______________________
For more tips on how to read nutrition facts labels and ingredient lists, check out this sample chapter from my book, Nutrition Diva’s Secrets for a Healthy Diet: What to Eat, What to Avoid, and What to Stop Worrying About
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{ 16 comments… read them below or add one }
it’s useful, thank you very much.
Thank you very much , learning every day!
Spectacular post, clear and simple, easy to understand! Just what I needed. Thanks.
Ok so now how much is .3 mcg in I.U?
Clay, as I (tried to) explain above, it depends on the nutrient. 0.3mcg of WHAT?
seems u have asked for vit A i.e. 1 IU
So are you saying 300 mg. is 300 IU?
Any conversion for vitamin B-12 at 1000 IU to mcg?
I’ve never seen B-12 measured in International Units.
My doctor just suggested I take 1000 IU daily of vitamin B12 so I am also interested in the IU to MCG conversion for B12?
Check with him but I bet he meant to say mcg. 1000mcg is a fairly common dose of B12. I’ve never seen B12 given in I.U.s.
I bought a bottle of Blackmores B12 recently and found it was measured in 100 ug. I assume ug is international units. I would also like to know how much I am taking in mg as I don’t want to take too much.
I have just discovered that ug is not International Units. Sorry to waste your time.
So, not sure if you’ve already found the info you were looking for, but for future reference (because it can get confusing to consumers) …”µg” actually refers to micrograms (” µ” with a tail on the front representing “micro” or .000001)…which is 1/1000th of a “mg” (milligram). Therefore 100ug B12 x 1/1000 = .1mg of B12 in your supplement.
The National Institutes of Health recommends a daily allowance (RDA) of 2.4mcg ( another abreviation for microgram or “µg”) for females age 14+ per day; however oral B12 is notoriously not absorbed well by the body (especially unmethylated forms such as cyanocobalamine). Therefore, supplemental dosages are typically calculated to factor in excretion of b12 via bowel movements. You should speak with your primary care physician or clinical nutritionist in order to determine the best dosage for you though, because it really depends on your physical health, age, and/or if you have any existing conditions/diseases.
But to dispel any angst…several adults are b12 deficient and are not aware although they consume the RDA of b12. In addition, b12 has low toxicity due to its water-solubility, so extra b12 naturally leaves the body via excrement.
I know this is a lot of information for a simple question lol, but I do wish government health agencies would use more succinct methods of informing the general public about how to interpret what we are consuming. I could only imagine the discouragement many experience while attempting to decipher this info from any of the sources listed on the USDA website.
If this information aids any others who read it, that was my intent. Hope that helps!
Thank you very much PR, your information is very helpful.
Why is there IU? I don’t understand whats the reason!! So u saying 1 iu is .3 of A.. And .025 of D.. right? I have fracture.. I’m on a need to knw bases