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Description
Doctors Best L-Theanine with Suntheanine 150mg 90sDoctor's Best L Theanine with Suntheanine is the premier, patented form of the amino acid L theanine. Suntheanine is the purest form of L theanine on the market today. Helps promote a relaxed state without drowsiness Helps ease stress and everyday nervous tension. Helps promotes a positive mood and alertness. Helps to enhance cognitive performance Helps to diminish normal symptoms of premenstrual syndrome (PMS) Each Capsules Contains: Suntheanine L
Doctor's Best L-Theanine with Suntheanine is the premier, patented form of the amino acid L-theanine.
Suntheanine® is the purest form of L-theanine on the market today.
- Helps promote a relaxed state without drowsiness
- Helps ease stress and everyday nervous tension.
- Helps promotes a positive mood and alertness.
- Helps to enhance cognitive performance
- Helps to diminish normal symptoms of premenstrual syndrome (PMS)
Each Capsules Contains:
Suntheanine® L-theanine 150mg
Other ingredients: microcrystalline cellulose, modified cellulose (vegetarian capsule).
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4.6 ★★★★★
Based on 1329 reviews
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Product Reviews
★★★★★ 5
Quality product
Seeing as it passed the smog test without any issues, it seems this product worked exactly as intended.
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Reviewed in the United States on May 20, 2026
★★★★★ 5
So far so good
It seems to be working well, so far. The check engine light turned off and the my vehicle seems to be running well. Be sure to follow the instructions. A while back, I wasted some money on a different catalytic converter cleaner because I put the cleaner in on a full tank of gas. It's best to wait until you're at a half tank or less of gasoline before you put in your catalytic converter cleaner. Also, I drove around right after I put in the catalytic converter cleaner and before I filled up my tank again. A couple of days later, I went to the gas station and topped off my tank. Again, it seems to be running well for now.
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Reviewed in the United States on April 21, 2026
★★★★★ 4
Works ok for some stuff.
I tried this mainly to clean my cats. It sadly didn't work for that at all.
It did however work great as a basic fuel system cleaner. It smoothed out my idle and cleaned my O2 sensors they were a bit lazy before using this product now they switch fast like they are supposed too.
In terms of my recommendation I say use as a fuel system cleaner. Or if your cats aren't too clogged in my case I bought an old neglected used car that likely had that problem for years. So I don't think any pour in tank cleaner would work in my case.
However if your car just started having cat issues. This might work??
I think it's worth a try at least and isn't much more expensive than a basic fuel system cleaner so why not?
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Reviewed in the United States on May 16, 2026
★★★★★ 5
PASSED MY INSPECTION! THIS PRODUCT WORKS LIKE A MIRACLE DONT HESITATE TO BUY IT!
Inspection on my car due the end of January! My check engine light was coming on so I checked with a code reader & found it was a P0420. Read about the Catalytic Converter System possibly being in need of replacement or perhaps clogged. I am a woman, and know next to ZERO about cars, but I can read. Did investigate and found that the replacement of a Catalytic Converter system is mad expensive- also found this Moly Cleaner to add to gas tank. I'm not going to lie; I was nervous as I have a Kia Rio 2014 that has a very small gas tank and gets great gas mileage. In reading the consensus seemed to be to add to 1/4 tank of gas and drive fast for good periods of time to blow out the clog (if it was a clog). Did I mention I live in NYC and driving for long periods of time at high speeds can be a problem because of terrible traffic. Anyhow, this Saturday I poured the can into my 1/2 filled tank and hit a parkway near my home early morning. I did drive for 45 miles sometimes at 80mph then 60mph but tried to do it for a good few minutes at a time without getting pulled over. Checked my reader again, and it was not quite ready but the engine light did stay off. Next day, drove to work, stuck in traffic somewhat & never made it over 20mph & checked my reader again- all good to go for inspection. Went last night- my car PASSED and got that sticker in my window- so I am good for another year. The BEST money I have spent all year. Thank you for carrying this product! Saved me thousands! DONT HESITATE TO USE THIS. The hardest part for me was removing the cap on the can!
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Reviewed in the United States on January 13, 2026
★★★★★ 5
Great stuff
Seemed to work as well as or better than some more expensive catalytic converter cleaners. I put it in while at 1/3 tank and my Check Engine light went out almost immediately once I started driving. My Tundra has almost 230,000 miles and still runs great but was getting a little harder to start after I switched from full synthetic oil to conventional. I’ll never do that again and immediately switched back but the damage was done. Check engine light came on and I had to crank longer to get it started. Adding this Liquid Moly fixed both issues temporarily. I have to wonder if this was used regularly, say every 3 months, if it would clean the catalytic converter more permanently?
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Reviewed in the United States on December 29, 2025