Great
Based on 95 reviews
Z-STACK4.1Honesty, pricing, process and quality scores appear once 5 customers have rated them.
Zelenko Labs, built on the legacy of Dr. Vladimir Zelenko, creates products with purpose, precision, and integrity. Every formulation is made with high-quality ingredients and consistent standards, so you can feel confident in what you’re using. Thoughtful, reliable, and principled — Zelenko Labs products are made for people who care about quality.Our All American customer service team is here to help Monday through Friday, 9 AM to 5 PM EST — just give us a call at 1-800-ZELENKO (1-800-935-3656) or email our team at [email protected]
Z-STACK (zstacklife.com) has 95 customer reviews on Folks Told, with an average rating of 4.1 out of 5.
Showing 71 reviews with 5 stars · Clear filters
Stephy D.
Been using Z-Stack and Z-Night and really like both. Z-Stack feels like solid daily support, and Z-Night helps me relax and sleep better without feeling groggy. Clean formulas, all natural, brand I trust. Would recommend.
Reply from Z-STACKFeb 5, 2026
Thank you Stephy! Wishing you a fabulous 2026!
Kathy
I've been taking Z-Stack for close to 4 years and have not been sick one day since I started taking it. I am 72 years old, and full time daycare for a granddaughter in school so the germs do come home, but she also has not been sick since she started taking the Kid's Z-Spike gummies. I DO NOT understand all the bad reviews unless they are bots or angry people in general. I have needed to contact customer service MANY times and always (during business hours) get a live person with NO foreign accent, and they are always more than helpful! For those who are having problems with customer service, perhaps you're calling a wrong number. Their customer service # is 800-935-3656 and I NEVER have an issue with getting a wonderful representative. The product itself is a godsend. Miraculous to NEVER get sick at 72 years old in the 4 years I've been taking it. IGNORE BAD REVIEWS! Not true!
Valued Customer, NY, N.
I started taking Z Stack as part of Dr. Zelenko's prophylactic Covid protocol, as soon as it became available. I am unvaxxed, did NOT get Covid and did not get any flu or respiratory infection. I'll take these as long as they are available.
Linda M.
I've been taking 2/daily Z-Stack (monthly auto-ship) since hearing Dr Zelenko speak several years ago. I am a frail 85# 75 yr old with advanced COPD/Bronchitis that has not had so much as a cold or a flair-up since & still going strong. Prior, I would have 3-4 severe, lengthy flair-ups annually. It's been a blessing for me.
Diane H.
I have been using zstack since it came out. Me, who is prone to bronchitis, colds and always sick have not been sick since I began. I recently ran out and I didn't reorder because I found out I am loosing my job in July to outsourcing to another country 😪 anyway I wasn't taking it for about 2 ,3 weeks and I got the worse upper respiratory infection and bronchitis that I have ever had. It is 11 days and I am only maybe 70 percent. Well I am now ordering my supply. I'll save money elsewhere, these are too precious!! God bless Dr Z and his team. May he RIP
Shannon H.
It’s nice to have around
Zach
Good product, high quality from a great source. Dr. Zelenko is a leader in his field
