Saturday, November 7, 2026 · Customer reviews of US businesses
The Fair Hearing score
Great
95 reviews
Z-STACKSelect a line to read only those reviews.
Honesty, 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 The Fair Hearing, with an average rating of 4.1 out of 5.
95 approved reviews, newest moderated first
Since taking Zstack I have stayed very healthy! Great product. I do add vitamin K3 to it. The response to inquiries is quick and respectful. I recommend.
By Joan K.
Response from Z-STACK· Aug 10, 2026
Thank you Joan!
your products and your people are wonderful. the website however is often hard for me to navigate without accidentally buying something twice or signing up for a subscription. nevertheless it will not stop me from buying your products because they are great and so are your employees thank you bhb
By Brandt H.
Response from Z-STACK· Aug 10, 2026
Thank you Brandt!
Customer service was very responsive and helpful
By Tammy
Response from Z-STACK· Aug 4, 2026
Thank you!
I receive Z-DTOX and Z-STACK from you for over 2 years. The products are great.They have helped to keep me healthy. When ever I have a question your staff is easy to reach and knowledgeable regarding your products. So thankful to have found your products. Marian
By Marian De La V.
Response from Z-STACK· Aug 2, 2026
Thank you!
Their shipping is super slow. It takes a month to arrive. I'm not happy at all.
By Muharrem
Response from Z-STACK· Jul 29, 2026
After looking into your order, we found that it was unfortunately lost in international transit to Australia. While this is uncommon, we recognize how frustrating it must have been to wait longer than expected. We're glad we were able to resolve the issue for you, and we appreciate your patience while we worked to make things right. We value your feedback and are continuously working with our shipping partners to improve the delivery experience and minimize situations like this in the future. Thank you for giving us the opportunity to resolve the matter.
The Kids Z-Stack vitamins are literally the best kids’ vitamins out there, and we’ve tried plenty! If you want to keep your kids healthy, these vitamins really work! My three children have been taking them for about three years now. I get the subscription, and it’s worth every penny. Each of my children had a minor cold maybe twice within the entire last school year. I’m talking two to three days of sniffles, nothing major that even required a doctor’s visit. My oldest son had seasonal allergies for years, but not anymore. We virtually never get sick anymore. Praise God!!! Thank you, Dr. Zelenko! Also, the mixed berry flavor is awesome! My kids love it and say it tastes like Skittles!
By Mary Melissa H.
Response from Z-STACK· Jul 27, 2026
Thank you Mary!
Excellent customer service! Grateful for the help and problem solving!
By Wendy
Response from Z-STACK· Jul 22, 2026
Thank you Wendy!
The zsleeep really makes a difference in my sleep!!! They are very responsive and helful
By Stacy B.
Response from Z-STACK· Jul 20, 2026
Thank you Stacy!
