Why are caffiene mints not working for me anymore?

Why are caffiene mints not working for me anymore?

So I use this mint, it has caffiene plus L Theanine which works great. But 2 hours ago, around 11 pm I popped in 3 of these and was in complete flow mode which means L Theanine worked but I am feeling drowsy now (1.23 am) which is weird because 1 mint has 50 mg of caffiene and I consumed 150 mg of caffiene.

I'm thinking of using another caffiene pouch I have but I don't want to so I'll just eat a spoonful of instant coffee powder which works well all the time and because I can't risk sleeping as I have a physics test today morning.

Did I just build some tolerance for caffiene?

Why are caffiene mints not working for me anymore?
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