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About this tool
Log glucose readings with meal context, see target-range badges, time in range, and an estimated HbA1c.
The Blood Sugar Log records each glucose reading against the context it was taken in — fasting, before a meal, two hours after a meal, bedtime or random — so it is judged against the ADA target band for that moment rather than one blanket number. It then reports your time in range against the 70-180 mg/dL zone, your average per context, and an estimated HbA1c from the ADAG regression A1c% = (average mg/dL + 46.7) / 28.7 over your last 90 days. It is a record to take to your care team, not a substitute for a lab test or for medical advice.
Open Blood Sugar Log & Tracker on AltFTool — it loads instantly in your browser.
In the Add a reading panel type the number into Reading, pick the unit with the mg/dL or mmol/L toggle, and choose a Context button — Fasting, Before meal, 2h after meal, Bedtime or Random. Each button shows its own target band, and a badge under the form scores your number against that band as you type.
Set Date, Time and an optional Note, then press Add reading. The row lands in Your readings and refreshes the Readings, Average and Time in range tiles for whichever window the 7 days, 30 days, 90 days or All filter is on, while the Est. HbA1c tile always works from the last 90 days. With nothing logged yet, Load a sample week fills in 20 demo readings across a week.
Take the log out with Copy log for plain text, CSV for blood-sugar-log.csv, or Print for a clinic sheet carrying the averages, time in range and every reading — all three follow the window filter and stay disabled while that window is empty. Clear all then Delete everything wipes the browser copy, and Cancel backs out.
A 140 two hours after lunch is scored in range while a fasting 140 is not, because each reading is judged against its own ADA band.
Splits your readings into very low, low, in range, high and very high bands so a flat average does not hide swings in both directions.
Readings are stored in mg/dL and converted for display using the 18.0182 factor, so toggling to mmol/L and back does not round your history away.
A commonly cited goal for many adults is more than 70% of readings inside 70-180 mg/dL (3.9-10.0 mmol/L), with under 4% below 70 mg/dL and under 1% below 54 mg/dL. This log calculates exactly those bands from your entries. Your own targets can be tighter or looser — pregnancy, older age and hypoglycemia unawareness all change them, so confirm yours with your care team.
It uses the ADAG study regression: A1c % = (average glucose in mg/dL + 46.7) / 28.7, applied to the average of your readings over the last 90 days, since that roughly matches the lifespan of a red blood cell. Treat it as a signal only — finger-stick readings are a biased sample that skips the overnight hours, and anaemia, pregnancy, kidney disease and haemoglobin variants shift real lab A1c independently.
Under 70 mg/dL (3.9 mmol/L) is hypoglycemia, and the standard response is the 15-15 rule: take 15 g of fast-acting carbohydrate such as four glucose tablets or 120 ml of juice, wait 15 minutes, and recheck — repeat if still under 70. Avoid chocolate and nuts, whose fat slows absorption. If someone is confused, seizing or unable to swallow, do not give anything by mouth; that needs glucagon and emergency help.
Fasting and pre-meal readings use the ADA band of 80-130 mg/dL, and two-hour post-meal readings use under 180 mg/dL, with 100 and 140 mg/dL marked as the tighter non-diabetes ideals. Bedtime uses a 90-150 mg/dL band to reduce overnight hypoglycemia risk. These are general adult figures, and only your clinician can set the ones that apply to you.