Experiencing the symptoms of "die-off" is the easiest, and surest, way to know that the candida is dying off. The first precondition is that you have been sticking to strict low carb with absolutely NO cheating. You start taking an anti-fungal agent and subsquently experience the symptoms of "die-off". Well, I think that you can be pretty certain that the anti-fungal is in fact, killing off the candia.
Generally you feel much worse when die off occurs. Of course you can control your level of die off so that symptoms ar bearbable, simply lessen the antifungal. But , your symptoms may become more extreme, you may feel tired, like you need more rest.
Since the symptoms of die off and the symptoms of candida can be identical , you can really only be sure it candida if in fact you have been on the diet and are doing everyhting necessary.
Example, I was bloated for months. Being bloated is a symptom of having candida. But any symptom of candia can also be die off , since both symptoms and die off are caused by a release of toxins by the candida. ( candida release toxins in a burst when they die). I knew that the bloating was die off and not candida because I was dilgent with my diet. So since I knew there was know way I was feeding it anything...it had to be die off. And then one day I woke up and the bloat was gone.
I also find that when I have die off I may feel tired , exhausted actually and worn down. I also have some symptoms. But usually my most bothersome symptoms will start to ease. A clear indication of die off. Some symptoms appear such as being tired but others such as vision problems start to go away.
When you are consistantly correcting the cause of the problem, ie fixing the overly acid state of your body back towards being alkaline bmo of an alklising diet assisted with a antifungal like Paramune+ or something similar.