On top of worse headaches now than before I started taking acetazolamide (750mg daily), I find that I am physically and mentally exhausted on a daily basis. 
It doesn't matter how much sleep I get, I will be at work and feel ok (well, apart from the usual; headaches, bulging vision etc), then literally one minute later I can barely keep my eyes open, my vision goes blurry and every time I stand up I feel like I've got headrush. It's not just tiredness, it's suddenly like I have run a marathon, done a double shift of a really heavy manual labour job (when I'm actually  just sat at a computer) and not slept for a week. It's actual exhaustion. 

My question is, is this a side effect of the Acetazolamide, or a side effect of the IIH? 
I see the neuro-opthamologist on 11th April,  and have a horrible feeling they will increase my dosage as I still have the whooshing in my ear and bulging vision, so would like to be prepared if this feeling is going to get worse if they do 

Thanks in advance.

well, I couldn't take Diamox because it gave me as much brain fog as I had from the IIH.
but there is a paper looking at ICP in "chronic fatigue" patients, showing that 20% met the criteria for a diagnosis of IIH and 85% felt better after removal of CSF.  I feel that exhausted when my ICP goes up.  I also have an adrenal problem and I think it is ultimately secondary to the ICP pressure on the pituitary, a sort of hormonal empty sella syndrome.  

you could also be describing "excessive daytime sleepiness" which is a symptom of obstructive sleep apnea.  OSA raises ICP.  my IIH got better when I started treating my OSA.  

so I don't know how to answer your question, you may have to sort this out on your own.  if the symptoms come on within an hour of the Diamox dose, it's probably the Diamox.

I agree with Deb, there are different causes even within the IIH diagnosis. If you haven't already, I'd start a symptom log with times you eat, take meds, and when symptoms occur. It may help you figure it out. I tend to hit a wall between 11am-2pm, so completely understand!