fatty15 does one thing: it delivers 100 mg of purified C15:0 in a vegan capsule, once a day. The concept is interesting and the product is clean and simple, but most of the supporting research is still in cells and animals, so treat it as a long-term experiment rather than a proven fix.
What we like
- Single ingredient: 100 mg of C15:0 per capsule, no blends or fillers to decode
- Vegan-friendly vegetable cellulose capsule made under US cGMP standards
- Low-commitment 30-Day Trial Kit before you move to a 90-day supply
- Free standard shipping and a 30-day money-back guarantee on first orders
- Optional at-home C15:0 blood test to see your baseline level
Keep in mind
- Human clinical evidence is still limited, and much of the research involves the co-founder
- Ongoing cost adds up for a single nutrient
- Guarantee does not cover subscription refills or annual kits
- Benefits, if any, are gradual and hard to feel day to day
Most supplement brands sell dozens of products. fatty15 sells, in effect, one: a purified form of pentadecanoic acid, a saturated fatty acid usually shortened to C15:0. It is the same odd-chain fat found in small amounts in whole-fat dairy, some fish and certain plants, and the company argues that many people simply do not get enough of it from a modern diet.
That narrow focus makes fatty15 easy to understand and easy to take, but it also puts a lot of weight on a single scientific idea. In our research we looked at what the capsule contains, what it costs over time, how the guarantee works and, most importantly, how strong the evidence behind C15:0 really is.
What C15:0 is, and why fatty15 is betting on it
The brand was co-founded by Dr. Stephanie Venn-Watson, a veterinary epidemiologist, and Eric Venn-Watson. Its origin story traces back to research on aging dolphins, where higher C15:0 levels were linked to healthier aging markers. From there, the team proposed that C15:0 behaves like an essential fatty acid: something the body needs but does not make in meaningful amounts.
fatty15 positions its capsule as support for cell membranes, metabolic health and healthy aging. The company describes C15:0 as activating cellular pathways such as AMPK and PPAR and dampening several pro-inflammatory signals. It also highlights GRAS (Generally Recognized as Safe) status for its ingredient, which speaks to safety rather than effectiveness.
The product itself is made from purified C15:0 rather than dairy fat, so it is suitable for people who avoid animal products, even though the nutrient is best known from butter and cheese.
The lineup: capsules, gummies and a blood test
The range is small and clearly organized.
- Original Capsules are the core product. Each vegan capsule holds 100 mg of C15:0, and the usual serving is one a day.
- Gummies for Adults deliver the same nutrient in chewable form for people who prefer not to swallow capsules.
- Gummies for Kids, a sugar-free mixed berry option, were listed as coming soon when we checked.
- The fatty15 Test is an at-home bloodspot kit processed through Genova Connect that measures your C15:0 level; the brand lists it as HSA/FSA eligible.
- Advanced Formula Extra Strength (AFEX) is sold only through approved healthcare practitioners and Fullscript.
There is also a book, The Longevity Nutrient, plus merchandise. For most shoppers, though, the decision is simply capsules or gummies.
See fatty15's current range
What the evidence does and doesn't show
fatty15 cites more than 100 peer-reviewed studies on C15:0, and that body of work is genuinely growing. The honest caveat is that much of it has been done in cell cultures and animals, and relatively few randomized controlled trials have tested C15:0 supplements in people. Independent reviewers have also noted that several key papers are authored or co-authored by the company's co-founder.
That does not mean the science is wrong, only that it is early. The brand's own customer survey reports that a majority of buyers noticed benefits within about 16 weeks, but survey responses are not the same as controlled data. If you try fatty15, it is sensible to give it a few months and judge it on measurable things, such as your blood test or lab markers your doctor already tracks, rather than on how you feel after a week.
Reported side effects are uncommon and mild, such as digestive upset or headache, but long-term data are still limited.
Cost, subscriptions and the fine print
The 30-Day Trial Kit sells for about $49.95, which works out to roughly $1.67 per daily capsule. The 90-Day Starter Kit is listed at about $149.95, and subscribing brings the per-day cost down to around $1.33, with recurring 90-day refills priced near $119.95. Adult gummies on subscription were listed at about $63.96.
Shipping within the US is free by USPS First-Class, with a paid UPS upgrade available on one-time orders. The 30-day money-back guarantee applies to eligible first purchases only; it does not cover annual kits or later subscription refills, so it is worth starting with the trial kit if you are unsure.
Promotional codes appear regularly on review sites and in the brand's newsletter, so check for a current offer before paying full price.
Who should consider it, and who can skip it
fatty15 makes the most sense for healthy adults who are interested in longevity nutrition, already have the basics covered (sleep, protein, movement, a varied diet) and want to add one well-defined nutrient rather than a large blend. People who like to track data may appreciate pairing it with the C15:0 blood test.
It is a weaker fit if you want quick, noticeable effects, need a broad multivitamin, or are on a tight budget. Anyone managing a medical condition, taking prescription medication, pregnant or breastfeeding should check with a clinician first. Parents should speak to a pediatrician before using any children's version.
A practical way to decide is to start with the 30-day kit, take the capsule at the same time each day with a meal, and keep a short note of anything you are hoping to change, such as energy, skin or routine lab results. If you want harder data, the blood test gives you a before-and-after comparison. If nothing meaningful has shifted after three or four months, it is reasonable to stop and put the money toward other basics instead.
If you are comparing longevity-focused brands, Timeline's Urolithin A and partiQlar's NAD+ precursors take different approaches to cellular aging and are worth reading about alongside fatty15.
Our verdict
fatty15 is one of the cleaner, more transparent products in the healthy-aging space: one ingredient, one dose, clear pricing and a reasonable first-order guarantee. What it cannot yet offer is a large base of independent human trials. If that trade-off is acceptable to you, the trial kit is an inexpensive way to find out whether it earns a place in your routine.
fatty15 products at a glance
| Product | What it is | Price |
|---|---|---|
| Original Capsules – 30-Day Trial Kit | A one-month supply of 100 mg C15:0 vegan capsules, taken once daily. | about $49.95 |
| Original Capsules – 90-Day Starter Kit | Three months of capsules; subscribing lowers the per-day cost and sets up refills. | about $149.95 |
| Gummies for Adults | Chewable C15:0 for people who prefer not to swallow capsules. | about $63.96 with subscription |
| fatty15 Test | At-home bloodspot test via Genova Connect that measures your C15:0 level. | — |
Prices as listed on the brand's site at the time of our research and may change. Check the store for current pricing.
fatty15 FAQs
Is fatty15 legit?
Yes. It is an established US brand co-founded by researcher Dr. Stephanie Venn-Watson, with clear labeling, free shipping and a 30-day first-order guarantee. The main open question is how strong the human evidence for C15:0 supplementation is, not whether the company is genuine.
How much C15:0 is in each capsule?
Each Original Capsule contains 100 mg of C15:0, and the standard serving is one capsule a day. Follow the label and ask your doctor before changing the dose.
Is fatty15 vegan?
The capsules are described as vegan-friendly and use a vegetable cellulose shell. The C15:0 is a purified ingredient rather than dairy fat.
How long does fatty15 take to work?
The brand's own survey suggests many users notice changes within about 16 weeks. Effects are gradual and vary, so plan on a few months before judging it.
Can I get a refund?
First-time eligible purchases are covered by a 30-day money-back guarantee. Annual supply kits and subscription refills are not covered, so start with the trial kit if you are unsure.
Healthy adults curious about C15:0 who want a simple, single-ingredient daily capsule
Disclosure: InhouseHeal may earn a commission if you buy through links on this page. Our score is based on research of the brand's products, evidence, pricing and policies. How we review.
