Is your IQ a fluctuating thing or is it a constant?

IQs can be constant or fluctuating. In normal cases, it might increase slightly with age, but no major fluctuations take place (if a reliable test is performed, consistently).

It cannot be an exact science as measure the brain power is beyond the intelligence of the humans. So we have to rely on the best we can.

There is always minor fluctuation in IQ, but in a good IQ test, you will remain relatively consistent. As you age, however, your IQ inevitably goes down (unless you continue to learn at a constant or increasing rate) because IQ is determined like this:

Mental Age/Chronological Age x 100

So if your mental age is 20 and your Chronological age is 10, your IQ is:

20/10 (=2) x 100 = 200. Thus your IQ is 200, or double "normal". Everyone (ideally) should have an IQ of at least 100, meaning they are mentally the same age as they are chronologically.

I've had my IQ tested three times over the course of my life (at 13, 16, and 20 years old) and my IQ has oddly stayed at approx. 136.

(I tested 136, 135, 136 . . . VERY close each time. ) This means I continued to learn and develop intelligence as I aged. That will likely not continue, however, and my IQ will probably get closer to 100 as I continue to age.

yeah, fluctuating depending on your condition, experience. Plus there is a measurement error. I think IQ accuracy is like +/-10

well, I can only speak for myself of course, but I find that, starting from friday nights, my IQ takes huge dive downwards, and it stays that way untill monday afternoon, in extreme cases even till friday afternoon. But that is truly extreme. Usually I am able to have a reasonably normal conversation again by tuesday morning.

fluctuating - depending on life circumstances

fluctuating, people always learn new things, otherwise we would have super babies!!!

good question.