See healthy,
lasting weight loss
The world's first handheld metabolic coach.
Clinically Validated · HSA/FSA Eligible
See healthy,
lasting weight loss
The world's first handheld metabolic coach.
Clinically Validated · HSA/FSA eligible
As seen on
How Lumen works
Most weight loss plans rely on generic rules — eat less, move more, cut carbs — even though your body changes every day. Lumen removes the guesswork with a weight loss program personalized to you.
See if you're burning
fat or carbs
Each morning, take a quick breath to measure your metabolism and see what your body is burning — fat or carbs
Follow your daily nutrition plan
Lumen translates your metabolic reading into clear guidance for eating, activity, and recovery that day
Burn more fat, lose weight, and keep it off
Track how increasing your metabolic flexibility helps you burn more fat and maintain lasting weight loss
Trusted by doctors and health experts
Hear why leading doctors and researchers recommend tracking your metabolism every day.
Backed by researchers at the world's leading institutions
The science isn't new.
The technology is.
Your body releases different amounts of CO₂ depending on whether it's burning carbs or fat. Lumen reads that signal in a single breath — so you can see how your metabolism is responding, day by day.
The gold standard
of metabolic science
Indirect calorimetry is the clinical method used in hospitals and research labs to measure metabolism. Lumen brings that same science into a single breath.
Your breath reveals
your fuel ratio
RER — Respiratory Exchange Ratio — is the ratio of CO₂ you exhale to O₂ you consume. When it's low, you're burning fat. When it's high, you're burning carbs. One breath tells the whole story.
From insight to
daily action
Your reading tells you whether to load up on carbs, lean into protein, or continue fasting — no guesswork. The right move for your body, every day.
What you get
with Lumen
Measure your
metabolism daily
One breath each morning tells you how food,
sleep, and movement affect whether you're
burning fat or carbs, and when to break your fast.
Eat for how your
body woke up today
Lumen builds a personalized daily plan
that shows you what to eat, how much,
and when. No calorie counting, no guessing.
Burn fat and
preserve muscle
Lumen spots when your body is at risk of
breaking down muscle and tells you what to do next. So weight loss comes from fat, not muscle.
Fuel your workouts
and recover smarter
Breathe before you train to see if your body
is ready to burn fat or needs carbs first.
Breathe after to see how it responded and
what your body needs to recover.
Train your metabolism
to burn more fat
Your metabolic flexibility score reflects
how flexible and healthy your metabolism is.
See how you burn more fat as your score
increases, week over week.
Get support from
the Lumen community
Share wins, ask questions, and get advice from
people on the same path. Real conversations with
real Lumen users, right inside the app.
40+ integrations
Sync Lumen with your favorite health apps and wearables for a seamless, data-driven experience.
Real people. Real results.
"My husband had watched me struggle with taking GLP-1 medication and thought [Lumen] would be a good alternative. It helped me understand what I should be eating when, and how it reflects in the fat-burning process."
Sharon lost 30 lbs coupling Lumen with GLP-1
"Great tool to live a healthy lifestyle and track my metabolism. This has helped me tremendously with my metrics and shed few pounds."
Nadia lost 3% body fat with Lumen
"Lumen has been a game-changer for me. It's empowering to have such clear, personalised information about my health and to finally understand the unique story my metabolism tells every day."
Amy lost 26 lbs on her
journey with Lumen
"Should not have waited to get this. In a short time I have been able to learn if my body is capable of losing weight. It is. So much information available. I wish I had done this sooner."
Don't waste
another breath
Get $20 off when you sign up to our newsletter
FAQ
How does Lumen measure my metabolism?
When your mitochondria use carbs as fuel, they release more CO₂ into your blood, and when they burn fat, they release less CO₂. Lumen analyzes the CO₂% in your breath and determines if you are using mostly fat or carbs for fuel based on the CO₂ concentration.
Is Lumen's technology validated?
Lumen's technology is validated by multiple peer-reviewed scientific studies and is proven to measure metabolism as accurately as the gold-standard metabolic cart. Read the peer-reviewed paper.
How does metabolic flexibility improve my health?
Metabolic flexibility refers to how efficiently your mitochondria switch from burning carbs or fats for fuel, depending on their availability and your body's needs. Being metabolically flexible can be critical for disease prevention and helps with managing weight, improved insulin sensitivity, higher energy levels, better sleep, and even longevity.
Do I need the Lumen device to use the premium app features?
Yes, the Lumen device and app work together. The Lumen device measures your metabolism through your breath in real-time and the app provides personalized insights and lifestyle guidance based on those measurements.
How can I pay for Lumen using HSA/FSA?
Select "Checkout with HSA/ FSA." If you are logged into Shop Pay, please select "Check out as guest."
Complete your delivery and billing details, and then click "Pay now."
From there, enter your HSA or FSA card details and complete your checkout as usual. If you don't have your card handy, you can enter in a credit card, and Flex will send you an itemized receipt you can submit to your provider for reimbursement.
Who is Lumen for?
Lumen is for adults looking to improve their metabolic health, manage their weight, boost their energy levels, support their workout routine, and live happier and longer lives.
The Lumen app is not available for use by individuals under the age of 18.
If you are pregnant, breastfeeding, or suffer from the following conditions, please consult a medical professional before using Lumen:
Diabetes
Severe asthma
COPD
Additionally, Lumen's nutritional recommendations may not be suitable for people with:
Kidney disease
Cancer
Thyroid disorder
Is there a warranty?
Yes, we offer a one-year warranty from the date the device is delivered to you. If your device or charging dock are damaged by manufacturing defects during that period, we'll fix or replace them free of charge. You can read our full warranty policy.
¹Customers' results have not been independently verified. Results vary. Always consult with your physician when starting or stopping a medication.
All medical services are delivered by licensed healthcare providers with independently owned and operated medical practices. Lumen does not provide clinical care of any type.
Lumen is a wellness device intended to offer generalized support for general wellness and lifestyle modifications. It is not a medical device, does not provide medical advice, and must not be used as a substitute for professional medical consultation, diagnosis, or treatment. Always seek the advice of a qualified healthcare professional with any questions regarding a medical condition or before making any changes to your diet, exercise, medications, or treatment plan.
* As reported in 2024 Lumen user data analysis
** https://pubmed.ncbi.nlm.nih.gov/36195053/
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