Log Blood Ketones in Loopa: Your GKI and What Moves With It

Key takeaways

• Loopa now logs blood ketone (BHB) readings from your meter, in mmol/L, with the time, the context and a note.
• Each reading is paired with a glucose reading to give your glucose ketone index (GKI), using the formula from the published GKI calculator.
• Metabolic Insights puts your ketones beside the food, fasting, sleep, exercise and weight you already log, and shows what tends to move together in your own data.
• Loopa shows no GKI target and no "good" or "bad" zone, and every pattern says how many readings it rests on.
• Metabolic Insights is part of Loopa Premium. Find it on the Health tab under Insights, or under Explore on the You tab.

If you use a blood ketone meter, the reading usually ends up in a notes app or on a scrap of paper, apart from everything that might explain it. Loopa now keeps it with the rest of your day. Log a ketone reading and Loopa pairs it with your glucose to give you a glucose ketone index, then lines it up with what you ate, how long you had been fasting, how you slept and how much you moved. Over time it tells you which of those tend to rise and fall with your ketones, and says just as plainly when nothing does.

What does a blood ketone meter measure?

A finger-prick ketone meter measures beta-hydroxybutyrate (BHB), one of the ketone bodies, in millimoles per litre (mmol/L). The liver makes ketone bodies when carbohydrate is scarce, during a fast or on a very low-carbohydrate diet, and the body burns them for fuel, including during exercise (Evans, Cogan and Egan, The Journal of Physiology, 2017). Because readings move with food, fasting and activity, a single number on its own says little. Readings logged beside those things over weeks say a lot more.

How do you log a ketone reading in Loopa?

On iPhone, open the Health tab, go to Insights and tap Metabolic Insights. The same screen is on the Health tab on Android, and both apps also list it under Explore on the You tab. On iPhone you can also search the Health tab for "ketones", "BHB" or "GKI".

Tap Log a ketone reading (or the + at the top) and fill in:

• Blood ketones (BHB): the number from your meter, from 0 to 10 mmol/L.
• Taken: now, unless you change it.
• Context: fasting, before or after a meal, before or after exercise, bedtime, on waking, or other.
• Glucose for the GKI: automatic, enter one, or choose one (more on this below).
• Note: anything you want to remember about it, up to 280 characters.

Apple Health and Health Connect have no blood ketone type, so ketones are entered in Loopa. Glucose, sleep, activity and weight from your connected sources are used as they arrive. If you test at the same times each day, set a Ketone check reminder from the same screen, and its notification opens straight to the entry sheet.

What is the glucose ketone index (GKI)?

The glucose ketone index is the ratio of your blood glucose to your blood ketones, with both in mmol/L. It was described by researchers who built a GKI calculator to follow metabolic therapy in brain cancer, and their formula is glucose in mg/dL, divided by 18.016, divided by ketones in mmol/L (Meidenbauer, Mukherjee and Seyfried, Nutrition & Metabolism, 2015). Loopa uses that formula exactly, so a glucose of 90 mg/dL with ketones of 1.0 mmol/L gives a GKI of 5.0, the same answer the published calculator gives.

The GKI is still being studied. A 2026 paper proposes it as a biomarker for monitoring nutritional ketosis in disease prevention and management (Lee and colleagues, Frontiers in Science, 2026). An accompanying commentary calls it a compelling hypothesis that still needs clinical validation, warns against treating it as a lifestyle prescription, and recommends n-of-1 studies, which follow one person's own readings over time (Bischof, Frontiers in Science, 2026). That is why Loopa shows your GKI with no target range and no colour for good or bad. It is a number about you, to compare with your own earlier numbers.

How Loopa finds the glucose for your GKI

A GKI is only meaningful when the glucose and ketone readings were taken close together, so you choose how the pairing works:

• Automatic (the default): Loopa uses your nearest glucose reading within 15 minutes, or within 30 minutes if there is none closer. With no glucose reading in that time, there is no GKI.
• Enter one: type the glucose from the same test, in mg/dL or mmol/L. It is also saved to your vitals.
• Choose one: pick from the glucose readings within 30 minutes, each shown with how many minutes away it is and where it came from.

If no glucose reading is close enough, the GKI says "No data" rather than guessing. Edit or delete the glucose reading later and the GKI updates with it.

What does the Metabolic Insights screen show?

The screen starts with four cards: your latest Ketones (BHB), Glucose ketone index, Glucose and Fasting, each with when it was taken, where it came from and a plain trend. A card with nothing to show says "No data". It never shows a zero you did not log.

Below them, Your 30-day baselines gives your own medians for ketones, GKI, glucose, sleep, resting heart rate and weight. They are compared with nobody else's. Heart rate variability has a line too, and it reads "Not available" for now, because no connected source sends it to Loopa yet.

Tap any reading to see the day around it: whether you were in a fast you timed in Loopa, how long since your last meal, the net carbs, carbs, fibre, protein, fat and energy you logged in the 24 hours before, your sleep the night before, your resting heart rate, exercise in the 24 hours before, steps that day and your nearest weight.

How do the trends and comparisons work?

Trends and comparisons has three views, over 7 days, 30 days, 90 days, 6 months, a year or dates you choose:

• Trend: one measure on its own. Choose from ketones, GKI, blood glucose, weight, sleep, net carbs, calories eaten, fasting hours, exercise minutes, resting heart rate or steps.
• Compare: two to four of those measures stacked on the same dates, each on its own scale.
• Scatter: your ketones or GKI against one thing, such as net carbs in the 24 hours before, sleep, fasting duration or weight change over 7 days, with how many readings were paired.

How does Loopa find what moves with your ketones?

What moves together checks your ketones and GKI against food in the meal before, over the previous 6, 12 and 24 hours and on the previous day, exercise in the 1 to 24 hours before, last night's sleep, how long you had been fasting and your weight. These are the things research ties to ketones and glucose: exercise at the start of a fast raised BHB over a 36-hour fast in a randomised trial (Deru and colleagues, Medicine & Science in Sports & Exercise, 2021), and five nights of short sleep changed glucose metabolism in healthy young men (van Leeuwen and colleagues, International Journal of Endocrinology, 2010). Studies like these describe groups of people. The explorer looks only at you.

Run enough comparisons on anybody's data and a few will look meaningful by chance. Loopa corrects for that with the Benjamini-Hochberg method, a standard statistical adjustment for testing many things at once (Benjamini and Hochberg, Journal of the Royal Statistical Society, 1995). The wording on each pattern follows the numbers:

Tap Why am I seeing this? on any pattern for the details: what was compared, the time window, how many readings it rests on, how many were missing and which method was used. A reading with nothing logged in a window is left out of that comparison rather than counted as zero. When nothing stands out, the screen says so: "That is a result too."

A pattern describes readings that tended to go together. It does not show that one led to the other, and Loopa never suggests changing your food, fasting, exercise or medication because of one. Research on ketogenic eating is mixed: an umbrella review of trials found high-quality evidence for some effects and low-quality evidence for most others (Patikorn and colleagues, BMC Medicine, 2023). Your own data is one more reason to have that conversation with your clinician, not a replacement for it.

Can you share your ketone readings with your clinician?

Yes. Export readings (CSV) builds a spreadsheet of your readings with the time, BHB, context, source, paired glucose, GKI, how it was paired, fasting duration and your note (the last year on iPhone, the last 90 days on Android). You can also add a Metabolic Insights section to the report you share with your clinician. It is off until you turn it on.

If you use Loopa's Help Me coach, it can talk through your trends and the patterns Metabolic Insights found. It receives a few sentences describing your trends and patterns, never the readings themselves.

Is Metabolic Insights free?

Metabolic Insights is part of Loopa Premium, along with ketone logging, the GKI, trends and comparisons, What moves together and the export. New members get all of Loopa Premium free for their first 14 days. On Loopa Basic the row shows a Premium badge, and tapping it shows what Premium includes. See Loopa pricing for the plans.

If your Premium membership ends, Metabolic Insights locks and nothing is deleted. Rejoin and every reading and chart is where you left it.

Questions people ask

Does Loopa sync ketones from my meter or my watch?

No. Apple Health and Health Connect have no blood ketone type, so ketone readings are entered in Loopa. Glucose, sleep, activity and weight from your connected sources are used automatically.

What is a good GKI?

Loopa does not say. Published GKI zones came from brain cancer research and are still being validated, so Loopa shows your GKI next to your own earlier readings and leaves what it means for you to a conversation with your clinician.

Why does my GKI say "No data"?

There was no glucose reading within 30 minutes of the ketone reading, or the ketone reading was 0, which cannot be divided by. Enter the glucose from the same test, or choose a nearby reading, and the GKI appears.

Does Loopa work for a keto diet or fasting?

Metabolic Insights works with whatever you already log in Loopa. Fasts you time with the fasting timer, the food you log and your connected sleep and activity all feed the same screen.

Metabolic Insights shows what seems to happen in your own data. It is not medical advice.