Choosing keto for the food side of this changes the experience in ways worth knowing in advance, because it is a genuinely mixed thing and most accounts only give you the flattering half. Knowing the full picture means none of it catches you off guard.
The physical signs
Several changes are common once your body shifts to running on fat. Your sense of taste changes, and your mouth can taste metallic. When you wake, especially if you are also fasting, you may notice a faint sound or a kind of vibration in your ears. There is often a low background sense of your body being under some strain, and oddly that can sit next to something almost satisfying, because you know the strain is your body burning its own fat rather than sugar. None of these is a problem on its own. They are the markers of the change rather than warnings.
Sleep is the one to watch
For some people keto disturbs sleep, at least early on. You might struggle to drop off, or wake very early, tired and wired at the same time. It usually settles within a week or two as your body adjusts. If it does not, that is worth taking seriously rather than pushing through indefinitely, because sleep affects everything else you are trying to do.
The claim worth being honest about
A lot of keto content promises mental clarity, the idea that you think faster and sharper without carbohydrates. Maybe there is something to it. The honest position is that it is hard to tell. The clear-headed feeling is tangled up with everything else going on, the early waking, the afternoon dip, the novelty of doing something new, and separating a real cognitive change from that noise is close to impossible. So this guide will not promise you sharpness. Plenty of the other effects are real and easy to notice; that one is best left for you to judge, with no claim attached.
When to pay attention
Treat most of the discomfort as normal and expected. At the same time, ordinary discomfort and something being genuinely wrong are not the same thing, and keto is not an excuse to ignore a real warning. If something seems clearly off, beyond the signs described here, treat it as you would any other symptom and get it checked.