IQ is 1-150. People that have been attempted to test above 150 are all numbers that are based on assumptions.
Quite frankly, the world record of 230 is a load of crap. Up to 150 IQ can be tested in relation to the masses pretty well. But if you have 150 or 230, I wouldn't say there's that big a difference.
That said, one can practice IQ tests as well. For example the world record in IQ test person has scored many IQ's varying from 150's up to 230. Tbh, I'd go for the 150+ as her IQ.
I did an IQ test once when I was twelve and scored 116 and once when I was 18 and scored 136. But I've no idea what my exact IQ is. I don't think anyone has an exact IQ.