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Real-time metabolic feedback, tailored to your goals
New from Lumen
Your Body State: your metabolism, live
How you eat, move, and recover drives your metabolism, but until now, you couldn't see how your body was actually responding. Lumen measures your fuel burn in a single breath and gives you immediate, actionable guidance to optimize fat loss, balance energy, and strengthen your metabolic health, it’s called your Body State.
From signal to action
Actionable insight,
right when you need it.
Breathe
One guided breath. Lumen's CO₂ sensor reads whether you're burning fat or carbs right now.
Understand
Your breath, sleep, meals and workouts become one Body State: what's happening, and why.
Act
One next best action (eat, move, fuel or recover), timed while it can still change your day.
Track
Every breath moves the needle. Your live compass shows if you're on track to metabolic health.
The missing link
Everything you already track,
finally adding up
Your ring sees sleep. Your watch sees load. Your log sees meals. One breath into Lumen shows what it all did to your body — fat burn or carb burn — and what to do about it today.
Get Lumen
works with
The proof behind the experience
Trusted by doctors and health experts
Hear why leading doctors and researchers recommend tracking your metabolism every day
Real people. Real results.
Sharon lost 30 lbs coupling
Lumen with GLP-1
Nadia lost 3% body fat with Lumen
Amy lost 26 lbs on her
journey with Lumen
Gold standard
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.
RER
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.
Fat burn
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.
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.
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.
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.
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.
After adding your Lumen to the cart, select “HSA|FSA” as your checkout option, currently available only for annual or annual Duo memberships.
At checkout, Flex will prompt you to fill in a short health questionnaire to confirm your eligibility to pay with your HSA/FSA.
From there, enter your HSA/FSA card details and complete your checkout as usual.
If you don’t have an HSA/FSA card, you can complete the checkout with a regular credit or debit card, and Flex will provide you with an itemized receipt to submit for reimbursement.
Lumen is for anyone looking to improve their metabolic health, manage their weight, boost their energy levels, support their workout routine, and live happier and longer lives.
If you are under 16 years of age, 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
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 here.
* As reported in 2024 Lumen user data analysis