Jamie W.
Very easy to use!
Very easy to use!
Response from Fat ScientistMar 15, 2026
Thanks Jamie!

Fat Scientist is a free online resource built for people using GLP-1 medications like tirzepatide (Mounjaro, Zepbound) and semaglutide (Ozempic, Wegovy). We specialize in tools and educational content for users of compounded versions of these medications, which come in multi-dose vials and require precise dosage calculations. Our suite of calculators helps users convert prescribed milligram doses into exact syringe units based on their specific vial concentration, calculate split doses for improved tolerability, estimate medication costs, and plan their treatment timelines. Every calculator is free, requires no account, and works on any device. We built Fat Scientist because compounded GLP-1 medications present a unique challenge. Unlike brand-name auto-injectors with pre-measured doses, compounded vials require users to do math that directly impacts their safety. A wrong calculation means injecting too much or too little medication. We believe nobody should have to guess when it comes to their health, and the tools to get it right should be accessible to everyone. Beyond calculators, Fat Scientist provides guides on topics like reading vial labels, understanding concentration values, proper injection technique, and navigating the differences between brand-name and compounded medications. Our FAQ library addresses the most common questions we see in GLP-1 communities, written in plain language without medical jargon. Fat Scientist is operated by Productist LLC. We are not a pharmacy, we do not sell medications, and we are not a substitute for medical advice. Our mission is purely informational — giving GLP-1 users the tools and knowledge to use their medications safely and confidently. We are funded by voluntary donations from our users, not advertising or affiliate deals, so our recommendations are never influenced by commercial interests. Whether you are just starting your GLP-1 journey or adjusting an existing regimen, Fat Scientist is here to help you get the nu
Fat Scientist (fatscientist.com) has 129 customer reviews on Five Star Index, with an average rating of 5.0 out of 5.
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Jamie W.
Very easy to use!
Response from Fat ScientistMar 15, 2026
Thanks Jamie!
DS
I have been using the dosing calculator and reverse dose calculator on Fat Scientist since beginning my peptide journey last year. This site is the best and has made dosing so easy and safe. I have piece of mind every time I inject thanks to Fat Scientist.
Response from Fat ScientistMar 15, 2026
Thank you! So glad both the dosing and reverse dose calculators have been useful since you started your journey. That peace of mind on injection day is exactly what we're here for.
Sharon M.
This app is one of the best apps I have ever used. I would be lost without it. It is intuitive and is packed with so much information. Not only can you calculate your medication, but you can learn about so many topics.
Response from Fat ScientistMar 15, 2026
Thanks Sharon! So glad the calculators and educational content have both been valuable to you — having it all in one place is exactly what we were going for.
Tabhata M.
Started using the calculator to confirm my dosing on Tirzepatide. Extremely useful and accurate website!
Response from Fat ScientistMar 15, 2026
Thanks Tabhata! Confirming your dose before you inject is always a good idea — really glad Fat Scientist has been useful for you.
Feline E.
When I first started compounded Tirzepatide, I knew nothing Jon Snow. Thanks to Fat Scientist I learned how to read my vials and had an easy way to establish dosing consistency and confidently! Fat Scientist has been a huge part of my journey and I recommend it to everyone! Thank you!
Response from Fat ScientistMar 15, 2026
Every good journey needs a maester — so glad Fat Scientist could fill that role for you, and really appreciate you recommending it to others!
Carol D.
Relieved any anxiety I had over choosing a correct dosage. Very informative information for anyone getting started with self-administered injections.
Response from Fat ScientistMar 15, 2026
Thanks Carol! Injecting yourself, especially at the start, is definitely kind of scary — so glad Fat Scientist could help remove some of that anxiety.
Brad M.
I’ve used Fat Scientist for my doses every week. I’m an RN and am fully capable of doing it on my own, but I use it anyway to confirm it before injecting medication into my body. It helps me feel safe knowing that I have such a sturdy confirmation tool.
Response from Fat ScientistMar 15, 2026
Thanks Brad! Very much appreciate the endorsement from a medical professional like yourself, and so glad to be of help.
James K.
For those using vials for their medication this is an absolute must have. Takes all the guesswork out of knowing the dosage.
Response from Fat ScientistMar 15, 2026
Thanks James! Vial dosing has so many variables... really glad Fat Scientist can cut through the guesswork for you.