What can you tell me about l theanine and about recommended supplement’s

L-theanine may help with sleep, stress, and caffeine-related jitters; the suggested amount depends on the intended use.

• Sleep: 100–200 mg about 30–60 minutes before bed may help with the transition to sleep and sleep depth. Some sleep guidance gives a broader range of 100–400 mg, but start with one supplement and assess your response. 1 2
• Caffeine-related jitters: 200–400 mg may help blunt caffeine’s jitteriness and anxiety. 3
• Other potential effects: It may modestly ease anxiety and improve attention, and has been associated with lower blood pressure and improved blood-vessel function and blood flow. 4 5
• High doses: Up to 900 mg per day was described as potentially safe, but it is a high dose and may cause substantial sleepiness. 6
• Vivid dreams and parasomnias: Avoid theanine for sleep if you have night terrors or sleepwalk, since it can intensify dreams; vivid dreams that disrupt sleep are also a reason to leave it out. 7 8

For supplements generally, prioritize behavioral sleep tools first, and consult a healthcare professional before adding or changing a supplement. 9