I noticed an effect when taking it with coffee, too. I just had some l-theanine as a supplement. I just drink coffee, so I didn't think much of taking it with coffee, so I didn't expect anything. It seemed to "smooth out" the effect of the caffeine. Rather than jittery, it turned it into smoother focus.

Just throwing my own anecdotal experience on to the pile: L-Theanine is very effective for me when taken with caffeine in a 2-1 ratio. As another commenter said, it "smooths out" the jitteriness of caffeine, and this scales up to 200-300mg of caffeine (400mg-600mg of L-Theanine). The focus it provides is the closest legal alternative to adderall that I've found.

If taken alone, it's also pretty good at providing a general reduction in anxiety. I was travelling internationally one time with a co-worker who had a very low grade anxiety attack. Due to the circumstances our options for getting him medication or seeing an actual doctor were limited. I offered him some L-Theanine and he LOVED it, he said it calmed him down just enough the rest of the trip that he wasn't concerned with having another attack. Obviously, this isn't medical advice and ideally he would have seen an actual doctor, but in this case it was really effective. I will say that taking it without caffeine comes with a bit of sleepyness. Definitely a potent combo when taken with Melatonin and a lot of OTC sleep aids will combine the two.

This article mentions that previous studies found L-Theanine has stronger effect on anxious subjects. Perhaps caffeine provides that.

Try it along with bulletproof coffee (grass fed butter and MCT Oil Powder in the coffee) and keto diet. My new favorite.

Are you taking the caffeine from coffee in pill form or in a cup? Also how long does this seem to last?

What is your coffee to theanine ratio?