The Headache

"« Your headache is getting worse. Is it an effect of the pills? »"

As John takes pills, he will start to get a headache. This headache is a warning that you are approaching the pill limit. After you hit the limit, John will pass out and you will end the day, thus progressing the game into the second part where John has to live with the changes caused by the X-pills. The headache comes with three warnings. They are, in order:

You have a light headache. - Three pills away from the limit

'''Your headache is getting worse. Is it an effect of the pills?''' - Two more pills

'''You broke into a fever. You're sweating all over. Maybe you should stop taking pills?''' - The next pill will the last!

Pill Limit
The Pill limit refers to how many pills John can take before the headache makes him pass out. However, not all pills count towards the pill limit, thus not progressing John's headache, and some can even extend the limit. Without extension, you can normally take 9 pills.

So if you take all three of your clear pills outside of the headache, the maximum number of pills John can take is 9. If you take all three of them during the headache but none of them consecutively, the maximum becomes 9 base +9, so 18. To get the maximum number of pills, you must take two clears consecutively while you are close to passing out and also take the third clear pill during the headache as well to get 9 base +3 +9, for a grand total of 21 pills. Of course these numbers do not include any of the pills John takes that are listed in the table as a +0.

Overdosing
While John has a headache, he is considered overdosing. During this time, many pill combinations can trigger new effects. You can pick up these traits and then cure John's headache with clears without losing them, but you will need to overdose again if you want to get more of these special traits.