Google’s Health Guardian Service Is Now Available for Fitbit Devices.

At the end of September, Google’s “Health Guardian” feature set was released for the Pixel Watch 3, 4, and 5 smartwatches , and it’s now available to Fitbit Air users in a new update. Google says the new features include reports on blood pressure trends and insulin resistance, a significant advancement for a wearable device. Here’s what we know about Health Guardian, including how to set it up and what to expect.

Is it really possible to measure insulin resistance with a wearable device?

Insulin resistance is associated with type 2 diabetes and can be an early sign that you’re approaching prediabetes or diabetes. When the body’s insulin receptors stop responding as strongly to insulin, the likelihood of high blood glucose levels increases.

Insulin resistance is typically measured with blood tests. For example, fasting glucose and fasting insulin levels are combined into a measure called HOMA-IR. If you’re concerned about insulin resistance or prediabetes, it’s best to consult with your doctor to find out what tests they recommend and what to do with the results.

The insulin resistance detection feature coming to Google Health, Google notes, is “not intended for medical purposes” and “not a pre-screening tool for diabetes.”

Google published a paper describing some of the testing stages that preceded the development of an algorithm for detecting insulin resistance. In the study, researchers asked people to use their Fitbit or Pixel Watch fitness trackers to record various metrics, including heart rate, heart rate variability, and activity. The paper is unclear on how the algorithm works and whether it will be useful for the general population, but Google apparently hopes it will be an interesting factor to track in the Google Health app.

Is it really possible to measure blood pressure with a wearable device?

Google also published a paper about its blood pressure measurement algorithm, though it hasn’t been peer-reviewed. Rather than explaining how the algorithm works, it describes how the researchers tried to figure out what their AI-powered model might look for. According to the paper, Google’s model performs about as well as clinical blood pressure measurements, but it’s unclear how useful it will be in the real world. For example, the study didn’t include people with heart disease, but I imagine many people with heart disease would be interested in their blood pressure readings.

Is Health Guardian a free service?

Last month, Google announced in a press release that the Health Guardian app, which includes data on insulin resistance and blood pressure trends, is available for free to Pixel Watch 3, 4, or 5 users. Fitbit Air users, the company added, will be able to get blood pressure and insulin resistance data “with a Google Health Premium subscription later this year.” “Later” is already here, as this feature for Fitbit users is included in Google Health 5.11 , available for both Android and iOS.

So, access to the service is free if you have a Pixel Watch, but not if you only have a Fitbit Air: Google Health Premium costs $9.99 per month. It’s unclear what happens if you have both devices; presumably, having a Pixel Watch will grant free access. In any case, other devices, including older Fitbit models, don’t appear to be included in the program.

How to get Health Guardian forecasts for blood pressure and insulin resistance

In version 5.09 of the Google Health app for Android, the Pixel Watch received the Health Guardian feature. The Fitbit fitness tracker received Health Guardian in version 5.11 for both Android and iOS.

You can set up blood pressure and insulin resistance tracking immediately after installing the new version of the Google Health app. I was able to set up insulin tracking by going to the “Health” tab and then tapping “Metabolism,” and I configured blood pressure in the “Heart” section. You can also adjust your sleep breathing in the “Respiratory” section. (Some European users will have access to the “respiratory distress” feature, but it’s not available in the US.)

Google announced that the insulin and blood pressure monitoring features will provide a monthly report on the first of each month, with the first report arriving on October 1st if you’ve provided your watch with enough data in the previous month. If you’re a Fitbit user and are just setting up this feature, you’ll receive your first report on November 1st. Here’s what’s required for the app to work:

• To obtain blood pressure results , you must wear the watch for five consecutive days in the previous month (i.e., in October to obtain results for November). Wearing the watch overnight is optional.

• For insulin resistance : You must wear the watch for seven days and nights in the previous month, but these days and nights do not have to be consecutive.

How effective is Health Guardian?

I set up both features immediately after the Pixel Watch update, but I didn’t have enough time to complete the full seven days and nights before the October report. This means I don’t have a result for insulin resistance. However, I do have a result for blood pressure dynamics: “Not high.” As a reminder, the watch can’t know your actual blood pressure, so it makes rough estimates based on data that may not reflect your actual blood pressure. However, my blood pressure is usually within the normal range during doctor’s appointments, so this at least wasn’t a surprise.

Even more confusing is the question of what to actually do with the results. If your watch shows that your blood pressure or insulin levels are normal, would you delay seeing a doctor or forgo treatments or lifestyle changes that were supposed to help you? If your watch shows something is wrong, would you believe it and perhaps spend extra time and money on testing? Pixel Watch users are discussing their results online, and their reactions are varied. One Reddit user writes , “I woke up to find that my blood pressure is way too high and apparently the insulin in my body isn’t doing anything. This is despite my last doctor’s visit and blood tests being completely normal.” Another said , “I got such a high insulin result this morning. I’ve really changed my diet for the last four months and have been going to the gym regularly. I’ve lost about 40 pounds this year. It’s really frustrating. I’m just wondering how accurate this is.” I wonder about that too.

More…