First: does your CGM write to Apple Health?
HealthAPI reads Apple Health, so it sees glucose only when your CGM app puts it there. CGM apps differ on this, so check before anything else.
| CGM app | Writes to Apple Health | What to know |
|---|---|---|
| Dexcom G7 and G7 15 Day | Yes, glucose | Turn it on in the Dexcom G7 app: Connections, Apple Health, Activate, then allow Blood Glucose. Readings reach Apple Health 3 hours late. |
| FreeStyle Libre 3 and 3 Plus (Libre app) | Check first | Abbott's Libre app shares readings through LibreView and LibreLinkUp. Neither is Apple Health, and HealthAPI can't read them. |
| Other CGMs and glucose meters | If their app writes Blood Glucose | HealthAPI reads Blood Glucose from Apple Health whichever app wrote it. |
To check: in the Health app, tap Browse and open Blood Glucose, then scroll down to Data Sources & Access. Your CGM app should be listed there. If it isn't, HealthAPI has no readings from it to show the AI.
What the AI reads
| What | How much per lookup | Good for |
|---|---|---|
| Daily average, low and high | Up to 365 days | Weekly and monthly averages, trends, comparing days |
| Single readings with their times | Up to 500 readings, within 31 days | Time in range, overnight versus daytime, the hours after a workout |
| Steps, workouts, sleep, heart rate | The rest of your synced data | Glucose next to the rest of your day |
Units: glucose comes through in mg/dL, even if your Health app shows mmol/L. Ask the AI to answer in mmol/L and it converts (mg/dL divided by about 18).
Readings add up fast. Dexcom says a G7 sends a reading up to every 5 minutes, so a full day is close to 300 readings, about one lookup. A year of daily averages takes one lookup; a week of time in range takes about seven. All of it is read only, alongside the rest of the 50 synced metrics.
Set it up in 4 steps
Send glucose to Apple Health
Turn on Apple Health in your CGM app (for Dexcom G7: Connections, Apple Health, Activate), and allow Blood Glucose.Install HealthAPI
Get it from the App Store and allow Blood Glucose when it asks for Apple Health access. It's in the Clinical category of Sync Settings, which is on unless you turn it off.Ask about your glucose
Start with “What was my average glucose this week?”, then try the prompts below.
Prompts that work
“How was my glucose this week?”
Lower than last week. Your average was 112 mg/dL, down from 118, and 81% of readings were inside the range you gave me. Overnight averaged 104 mg/dL.
Replace [low] and [high] with the range you and your care team use. The AI doesn't know it unless you say.
Daily and weekly averages
- “What was my average glucose each day this week, with the lowest and highest reading?”
- “Show my weekly average glucose for the last 8 weeks as a table. Is it going up, down or staying flat?”
Time in a range you choose
- “Using every reading from yesterday, what percentage was between [low] and [high] mg/dL, and how much was below and above?”
- “Do the same for each of the last 7 days, one row per day.”
Overnight and daytime
- “For the last 5 days, compare my average glucose from midnight to 6 am with the rest of the day.”
- “Which night this week had the lowest overnight reading, and at what time?”
Glucose and the rest of your day
- “Over the last 30 days, is my daily average glucose different on days with a workout than on rest days?”
- “Show my glucose reading by reading for the 3 hours after my last run.”
- “Is my average glucose higher on days after nights with less than 6 hours of sleep?”
- “Do days with more than 8,000 steps have a lower average glucose than days with fewer?”
Checks before you trust an answer
- “How many readings do you have for each of the last 3 days? Point out any gap longer than an hour.”
- “List the numbers you used for that answer, day by day.”
For a fuller picture of the nights behind those mornings, see analyze sleep with AI. To bring a summary to an appointment, see the one-page doctor summary.
Before you trust an answer
- Dexcom readings arrive 3 hours late. Add HealthAPI's own sync, which runs when you open it and in the background as iOS allows, and the newest readings are always behind. For your glucose right now, use your CGM app.
- Daily averages hide swings. A day's average, low and high take one lookup. Time in range and overnight questions need the single readings, so ask for them by name.
- Gaps change the math. A new sensor or a lost signal leaves hours without readings. Ask how many readings each answer used, and compare days with similar counts.
- Two sources double up. If two apps write the same glucose to Apple Health, readings can appear twice. Ask the AI to flag readings with the same time.
- Patterns, not decisions. HealthAPI and the AI apps aren't medical devices. Don't use an answer to decide on food, insulin or medication, and talk to your doctor about anything that worries you.
Questions
Does Dexcom G7 send glucose to Apple Health?
Yes. In the Dexcom G7 app, open Connections, tap Apple Health, tap Activate and allow Blood Glucose. Dexcom says the readings reach Apple Health after a three-hour delay, not in real time, for both the G7 and the G7 15 Day.
Does FreeStyle Libre 3 Plus work with HealthAPI?
Only if your Libre app writes glucose to Apple Health, because HealthAPI reads Apple Health. Abbott's Libre app shares readings through LibreView and LibreLinkUp, which HealthAPI can't read. In the Health app, open Blood Glucose and check Data Sources & Access: if your Libre app isn't listed, HealthAPI has no Libre readings to show.
Can I get my glucose in mmol/L?
Yes, ask for it. HealthAPI reads glucose in mg/dL even when your Health app shows mmol/L, and the AI converts it: mg/dL divided by about 18 is mmol/L. Give your range in the same unit you ask for.
How far back can the AI look?
As far back as your synced history goes: a year by default, or more if you choose a longer Import History in HealthAPI's Sync Settings. Daily averages cover up to 365 days in one lookup; single readings come 31 days at a time.
Does it use my daily requests?
Yes: each lookup is one request, and syncing from your iPhone never counts. Averages over weeks or months take one or two. Time in range and overnight questions need every reading, which is about one lookup per day of CGM data.
Can the AI tell me if I have diabetes, or what to do about a reading?
No. It can describe patterns in your numbers, but it can't diagnose anything, and its answers aren't for decisions about food, insulin or medication. Use your CGM app for current readings and alerts, and talk to your doctor or diabetes care team about what the numbers mean.
