Checking blood sugar without needles

How far are we from checking blood sugar without a needle, using light, radio waves, sweat, tears or breath?

The FDA has not authorised any smartwatch or smart ring to measure blood glucose, and in February 2024 it warned people not to use them for that purpose. Early studies have reported signals for radio-frequency and sweat-based approaches. The most advanced result in the sources reviewed is an interim, company-reported study of a radio-frequency sensor worn on the forearm, with a mean absolute relative difference (MARD) of 11.1% against venous blood. The sources reviewed do not establish a reliable link between sweat glucose and blood glucose. They do not cover tear or breath approaches.

AI illustration · Illustrative scene, not a photograph of the specific device or experiment.
WHERE WE AREEngineering prototypes

Getting closer. Prototypes exist, but not in real-world use.

A radio-frequency prototype has been tested in people in an interim clinical study reported in March 2024. Sweat sensors have been built and tested, but the sources reviewed do not establish a link to blood glucose. No smartwatch or smart ring has been authorised to measure glucose, and the sources reviewed report no clearance for any non-invasive glucose device. The accuracy figures so far come from single or interim studies. That fits engineering prototype rather than pilot.

The tech tree

Everything recorded on Vrulum that this future needs, oldest foundations at the top and the goal at the bottom. Lines show what each step requires.

What it takes: Checking blood sugar without needles Unlocked Being researched Locked
  1. 2012Smart contact lensesPilot and early commercial Unlocked.
  2. 2013Breath diagnosticsResearch and prototypes Being researched.
  1. 2024Interim clinical study of a non-invasive radio-frequency sensorDone Unlocked.
  2. Date not recordedSkin-piercing sensors that show glucose under the skinDone Unlocked.
  3. Date not recordedSweat-based glucose sensors built and testedIn progress Being researched.
  4. Date not recordedAccuracy reported by glucose range, time of day and rate of changeNot started Locked.
  5. Date not recordedRegulatory authorisation for a non-invasive glucose deviceNot started Locked.
  1. GoalChecking blood sugar without needlesGoalRequires: Smart contact lenses, Breath diagnostics, Skin-piercing sensors that show glucose under the skin, Interim clinical study of a non-invasive radio-frequency sensor, Sweat-based glucose sensors built and tested, Accuracy reported by glucose range, time of day and rate of change, Regulatory authorisation for a non-invasive glucose device. Locked.

The road so far

2 of 5 steps done, 1 in progress.

  1. DoneSkin-piercing sensors that show glucose under the skin

    Continuous glucose monitors that pierce the skin are FDA-authorised. The FDA's 2024 safety communication distinguishes these from smartwatches and rings, and notes that the warning does not cover apps that show data from continuous glucose monitors. [1]

  2. Done · 6 Mar 2024Interim clinical study of a non-invasive radio-frequency sensor

    Know Labs reported interim results from a clinical study in March 2024. The sensor was worn on the forearm and tested in people with prediabetes or type 2 diabetes who took an oral glucose tolerance test. It was compared with venous blood, and the overall MARD was 11.1% in 130 held-out paired readings. The company describes these as interim results, and the release does not mention peer review. [2]

  3. In progressSweat-based glucose sensors built and tested

    A 2022 review describes sweat glucose as roughly 100 times lower than blood glucose, with a time lag relative to blood glucose. It also says sweat rate, temperature and pH affect readings. It lists reproducibility and reliability across large population studies as challenges still to be addressed. [4]

  4. Not startedAccuracy reported by glucose range, time of day and rate of change

    Heinemann and colleagues (2019) argue that an overall MARD is not enough, and that MARD should also be reported by glucose range, for night and day, and for different rates of glucose change. The Know Labs result is one overall MARD from a single interim study with 130 held-out paired readings. [3][2]

  5. Not startedRegulatory authorisation for a non-invasive glucose device

    The FDA says it has not authorised, cleared or approved any smartwatch or smart ring to measure blood glucose on its own. Know Labs says it plans to submit its sensor to the FDA for clearance. The sources reviewed do not report an outcome. [1][2]

Why it matters

Many people with diabetes check their blood sugar with a finger prick or wear a sensor under the skin. A reliable reading without a needle would make checking easier. Wrong readings are a safety risk, because insulin doses are set from them, so accuracy matters more than convenience.

What stands in the way

  • Glucose in sweat is roughly 100 times lower than in blood, and the link between sweat and blood glucose is not established in the sources reviewed.
  • Sweat rate, skin temperature and pH change sweat glucose readings. The review says sweat rate and pH should be measured alongside glucose.
  • MARD results vary between studies and between individuals, and one overall MARD does not show performance across glucose ranges.
  • Glucose in interstitial fluid and in sweat lags behind blood glucose, which matters most when glucose changes quickly.
  • The sources reviewed do not show that any non-invasive device has the accuracy needed for insulin dosing. The FDA warns that inaccurate readings can lead to errors in diabetes management.

Signals to watch

  • A peer-reviewed publication of the Know Labs study, with full data.
  • A larger trial of a non-invasive glucose device that reports MARD by glucose range and time of day.
  • An FDA clearance decision on a non-invasive glucose device.
  • A published, validated relationship between sweat glucose and blood glucose across different groups of people.
  • Further FDA safety communications or warning letters about consumer devices that claim glucose readings.

Sources

  1. government report
    Do Not Use Smartwatches or Smart Rings to Measure Blood Glucose Levels: FDA Safety Communication
    U.S. Food and Drug Administration, 21 Feb 2024.
  2. company announcement
    Know Labs' Non-Invasive Glucose Monitor Achieves 11.1% MARD in Latest Clinical Research Study
    Know Labs, Inc. (filed with the U.S. Securities and Exchange Commission), 6 Mar 2024.
  3. review article
    Benefits and Limitations of MARD as a Performance Parameter for Continuous Glucose Monitoring in the Interstitial Space
    Lutz Heinemann, Michael Schoemaker, Günther Schmelzeisen-Redecker et al.. Journal of Diabetes Science and Technology, 19 Jun 2019.
  4. review article
    Challenges and Strategies in Developing an Enzymatic Wearable Sweat Glucose Biosensor as a Practical Point-Of-Care Monitoring Tool for Type II Diabetes
    Sook Mei Khor, Joonhwa Choi, Phillip Won et al.. Nanomaterials (Basel), 10 Jan 2022.

Last reviewed 21 Oct 2026.