How we reviewed this: this is a research-based review. We did not buy or test the product ourselves. We checked the official website, policies and independent customer feedback, and every fact below links to its source. Facts checked 2026-10-30. How we review · Affiliate disclosure: we may earn a commission if you buy through our links, at no extra cost to you.
Quick verdict
Lumen is a legit product from a real, venture-funded company, and most buyers like it. It is a handheld device you breathe into each morning. It reads the carbon dioxide in your breath and the app tells you whether your body is leaning on carbs or fat for fuel, then suggests what to eat that day.
The honest catch is accuracy. Lumen does not measure oxygen, so it is not the same as a lab metabolism test, and in the company’s own validation study its reading explained only about 23% of what the lab equipment measured. Treat it as a motivating daily nudge, not a medical test. Also know that the membership renews every year (listed at $149) unless you cancel.
Pros
- ✓ Real company (Meta Flow Ltd.) with $62 million in funding and years on the market
- ✓ Strong ratings: 4.3 on Trustpilot from about 4,600 reviews and 4.6 on the iPhone app
- ✓ Simple morning routine with a personalized daily food plan
- ✓ Can keep users motivated and more aware of carbs, sleep and fasting
- ✓ 30-day return window and a 1-year warranty
Cons
- ✗ Measures CO2 only, not oxygen, so it is not a true lab-grade metabolism test
- ✗ Modest accuracy: about 20 to 23% agreement with a lab cart in studies tied to the company
- ✗ Membership auto-renews yearly ($149 listed; one buyer reported $179) and fees are non-refundable
- ✗ Readings change with how you breathe, so technique matters
- ✗ Not FDA cleared; it is sold as a wellness product
Check Lumen’s current offer →
Affiliate link. Prices and offers change, so check the official page.
What is Lumen?
Lumen is a small handheld breath analyzer made by Meta Flow Ltd., an Israeli company founded by twin sisters Merav and Michal Mor, both PhDs in physiology and Ironman athletes. Each morning you take a slow breath in through the device, hold it for 10 seconds, and breathe out steadily. The app then gives you a “Lumen Level” from 1 (mostly burning fat) to 5 (mostly burning carbs) and builds a daily plan around it.
The app also offers fasting schedules, carb guidance and food logging, and connects with Apple Health, Garmin, Oura, Whoop and others.
Does Lumen actually work?
Lumen’s idea comes from real science. In a lab, a “metabolic cart” measures both the oxygen you breathe in and the CO2 you breathe out. That ratio shows whether you are burning mostly fat (around 0.7) or mostly carbs (around 1.0). Here is how Lumen compares:
- It only reads CO2. The company’s own validation paper says: “Unlike the metabolic cart, the Lumen device does not measure oxygen consumption.”
- It does catch big changes. In that study, Lumen’s reading went up after people drank 150 grams of sugar, and a later study found it differed between a week of low-carb and high-carb eating.
- But agreement is modest. Lumen explained about 23% of the variation in the lab measurement in the 2021 study, and about 20% in a 2023 study. That is well short of the homepage claim that it is as accurate as the lab equipment.
- The research is not independent. Every published Lumen study we found had company employees, advisers or company funding behind it.
- Breathing changes the result. Breathing faster before a reading can push the score toward “fat burning,” and long-term users report readings that shift by a level within minutes.
It also cannot tell whether the fat you are burning is body fat or fat you just ate, and it does not measure calories. A 12-week weight-loss study by the company had no comparison group, so it cannot show Lumen itself caused the weight loss.
Bottom line: Lumen is best used as a consistent personal trend tracker and habit coach. If it gets you eating better and sleeping more, that is a real benefit. Just do not treat a single reading as a lab result.
How much does Lumen cost?
| Option | Price on 2026-10-30 | Notes |
|---|---|---|
| Partner offer page we link to | $199.99 | Listed price in the affiliate network. Confirm what membership is included on the order page. |
| Lumen device on lumen.me | $349 | Shown against $448, with “first 12 months free” membership |
| Membership after the free period | $149 per year | Renews automatically at “the then-current price” |
| Newsletter discount on lumen.me | $20 off | Code offered on the brand’s site |
On the day we checked, the partner offer was about $149 cheaper than the brand’s own site. Lumen’s price has changed many times over the years, so check the current total, including the membership, before you pay.
The membership and refund fine print
- Auto-renewal: the membership renews every year at “the then-current price.” You must cancel at least 24 hours before the term ends, and “all Fees are non-refundable once paid.”
- Renewal reminders: Lumen only promises notice before renewal if the price changes. One Trustpilot reviewer said they were charged $179 with no warning email. Put a reminder in your calendar.
- Without a membership: devices bought after July 2023 still take unlimited readings and show your Lumen Level, but you lose the plans and history features.
- Returns: 30 days from delivery, in original packaging, refund minus shipping, and you pay return shipping. The shop page says “no questions asked,” but its own FAQ says the device must be unopened. Ask support to confirm in writing before you open it.
- Warranty: 1 year against defects.
Who should not use Lumen
Lumen itself tells people to check with a doctor first if they are pregnant or breastfeeding, have diabetes, severe asthma or COPD, or are under 16, and its safety page says it is not suitable for people with diabetes, metabolic disorders or lung disease. Lung conditions change how you breathe out CO2, so readings would not be reliable.
Lumen does not mention eating disorders, but dietitians warn that this kind of daily tracking can become obsessive. If you have a history of disordered eating, skip it or use it only with your care team. People on insulin or other glucose-lowering drugs should talk to their doctor before following low-carb or fasting prompts.
Is Lumen legit, or a scam?
It is legit. Meta Flow Ltd. raised a $62 million Series B in December 2022, the device has been sold for years, and it ships what it promises. It is not FDA cleared; its terms describe it as a wellness product that does not give medical advice or diagnoses. We found no BBB profile and no regulatory actions against it.
What real buyers say
Lumen scores 4.3 out of 5 on Trustpilot from about 4,600 reviews (75% five-star, 7% one-star) and 4.6 out of 5 on the iPhone App Store from about 6,500 ratings. Note that Lumen’s Trustpilot profile is a paid, claimed profile, which can invite reviews.
What buyers like: clear daily guidance, staying motivated, learning how food, sleep and exercise affect them, and an easy app.
What buyers complain about: surprise renewal charges, slow support, an incomplete food database, and readings that seem stuck on “burning carbs” or jump around.
Who should buy it, and who should skip it
A good fit if: you are healthy, curious about your habits, like data and daily coaching, and will remember to manage the yearly membership.
Skip it if: you want a medical-grade measurement, you have diabetes, a lung condition or a history of disordered eating, or you do not want another subscription.
Alternatives
- Dexcom Stelo: an FDA-cleared over-the-counter glucose monitor that shows how food affects your blood sugar, $99 for about a month or $89/month.
- Abbott Lingo: an over-the-counter glucose sensor, $54 for a 2-week plan with no auto-renewal.
- Keto-Mojo GK+ meter: measures blood ketones directly with a finger prick, meter about $38 plus strips.
- A lab metabolic test: clinics and some gyms measure both oxygen and CO2 for a true result; prices vary.
- A registered dietitian: often covered by insurance and personalized to your health history.
See the current Lumen offer →
Affiliate link. Prices and offers change, so check the official page.
FAQ
Is Lumen accurate?
Partly. It detects big shifts, like after a large sugary drink, but in studies tied to the company it explained only about 20 to 23% of what a lab metabolic cart measured, because it reads CO2 only.
Does Lumen need a subscription?
The device works without one for basic readings (for devices bought after July 2023), but the plans and history need the membership, listed at $149 per year after a free first year. It renews automatically.
Is Lumen FDA approved?
No. Lumen is sold as a general wellness product, not a medical device, and we found no FDA clearance.
Can Lumen help you lose weight?
It can help some people build better habits, but there is no controlled study showing Lumen itself causes weight loss.
What is Lumen’s return policy?
30 days from delivery, in original packaging, refund minus shipping costs; you pay return shipping. Confirm with support whether an opened device qualifies.
How much does Lumen cost?
On 2026-10-30, $349 on lumen.me and $199.99 on the partner offer we link, plus a membership listed at $149 per year after the first year.
Who makes Lumen?
Meta Flow Ltd., an Israeli company founded by twin sisters Merav and Michal Mor.
Sources
- Lumen shop page (price and membership)
- Lumen refund and return policy
- Lumen subscription policy
- Lumen terms of use
- Lumen warranty and safety
- Lumen FAQ
- Lorenz et al. 2021, Lumen validation study
- Roberts et al. 2023, Lumen low vs high carb study
- Today’s Dietitian: what RDs need to know about Lumen
- CSPI: can you hack your metabolism with Lumen?
- Lumen on Trustpilot
- Lumen app on the App Store
- MedCity News: Lumen raises $62M
- Dexcom Stelo
- Abbott Lingo