[illvm]

These units seem _incredibly_ low to me. Your skin can generate almost 3000 IU in just 15 minutes on the right day. Many doctors even recommend treatments of 150,000 IU or more, in one go to correct deficiencies (do not do attempt without a doctor's recommendation and supervision).

I do not doubt your experience, but it seems incredible to me that just a 5000 IU supplement gave you heart palpitations. Then again, I've also read many reports about incorrectly labeled products (e.g. milk, supplements, etc.) which contained far more D2 or D3 than what was written on the tin, causing toxicity.

[jerf]

GP may have had a "heart on the edge"; just because your heart is currently beating correctly doesn't mean that it may not be just a wee bit of disruption away from beating incorrectly. Or you could have a lot of safety margin. I don't know whether medical tests could distinguish the two but just in day-to-day life there's very little way for you to tell the difference. (I wish I could; it would help me a lot.)

It is completely possible for "more of a good thing" to have a negative impact on you because it pushes something out of balance beyond what homeostatis can maintain. In principle the best solution is to go get more of what you need to balance it, but that can be easier said than done. Between the things that science still just plain doesn't know and the chaff of all kinds of garbage information about nutrition on the internet it can be very hard to figure out what you need.

[paulirwin]

I appreciate your respectful skepticism. It is entirely possible that the supplements contained significantly more than on the label. However, I'd like to point out that the generally recommended dose for supplements is only 800IU in adults, with up to 4000IU only in the case of Vitamin D deficiency. The "tolerable upper intake level" is 4000IU [1]. I am unable to track through Wikipedia's sources here at the moment, but that aligns with the parent of my original comment which I believe is in a peer reviewed journal. I would imagine that number was determined due to people like myself not tolerating amounts above 4000IU.

1: https://en.wikipedia.org/wiki/Vitamin_D#Dietary_intake

[mixmastamyk]

The original RDA of 800 was designed to combat Rickets and has recently been thought to be significantly too low for folks in higher latitudes. Given the high number of variables perhaps simple RDA guidelines are not practical.

I take roughly 5k per day in the winter and it has helped a lot. See my other post for details.

[trevorkoob]

Curious about your source for 3000 in 15 - I have read and reported more, and would like to read your source.