What do the symbols and HI/LO messages on a blood glucose meter mean?
Find it by its shape. 1. Pick what you see on the meter’s screen. 2. Match the drawing. Each symbol here is backed by the manuals of at least two different maker groups (Roche Accu-Chek, LifeScan OneTouch, Ascensia Contour, Abbott FreeStyle), and every number and every piece of health wording is quoted with the name of the maker that printed it.
Check your meter’s manual — makers differ.
Tap a shape — the symbols that use it appear here.
Letters — 5 symbols
HI on the meter (above the measuring range)The letters HI where the number would be, sometimes flashing with…LO on the meter (below the measuring range)The letters LO where the number would be, sometimes flashing with…Error code (E-1, E 1, Error 1)The letter E, or the word Error, with a number, shown instead of a…Thermometer or temperature message (too hot or too cold to test)A small thermometer beside the result on the FreeStyle Freedom…Memory and averages (mem, avg, logbook)The letters mem, or davg with a number of days, on the FreeStyle…
Blood drop — 1 symbol
Apple — 3 symbols
Before-meal marker (an apple)A whole apple, usually solid, with a stalk and a leaf, beside the…After-meal marker (an apple core)An apple core — the eaten apple, narrow in the middle with the top…Fasting marker (a crossed-out apple or circle)On the Contour Next One, an apple outline crossed out with a line.…
Bottle — 1 symbol
Thermometer — 1 symbol
Battery — 1 symbol
Arrows or colours — 1 symbol
Before you trust any chart, including this one
No published standard we could check defines the symbols on a glucose meter’s screen. The standards for these meters cover how accurately they measure (ISO 15197) and the marks printed on the packaging (ISO 15223-1), not what the display shows, so every meaning on these pages is taken from makers’ own manuals.
- HI and LO are not readings. They mean the result fell outside what the meter can measure, and the edge of that range differs by model: HI starts above 600 mg/dL on the Accu-Chek Guide, Contour Next One and OneTouch Verio Flex manuals read, but above 500 mg/dL (27.8 mmol/L) on the FreeStyle Freedom Lite.
- The same letters can mean something else. On the OneTouch Verio Flex, HI.t and LO.t mean the meter itself is too hot or too cold to test, not that your glucose is high or low.
- An apple is the before-meal marker on Accu-Chek, Contour and OneTouch meters, and an apple core the after-meal one. The marker only labels a result; it changes which target range the meter compares it with.
- Colours do not agree: on the Contour Next One a red light means below target, while on the OneTouch Verio Reflect red means above range and blue means below.
- Every manual read tells you what to do after a HI or LO in its own words, and those words differ. Each page quotes them and names the maker; none of it replaces the plan your healthcare team gave you.
Maker by maker
- Roche (Accu-Chek). The Accu-Chek Guide user manual (US, mg/dL) and Roche’s Accu-Chek Guide error-code pages read. Its screen uses words and small icons: an apple and an apple core for meal comments, a circle with a slash for fasting, a bottle with a C for control results, arrows for above and below target, and E-1 to E-14 for errors.
- LifeScan (OneTouch). Two US owner’s booklets read, the OneTouch Verio Reflect and the OneTouch Verio Flex. The Verio Reflect writes its warnings in words (EXTREME HIGH GLUCOSE, Temperature too high) and uses a coloured range bar; the Verio Flex uses HI, LO, HI.t and LO.t and a Range Indicator Arrow pointing at a colour bar under the screen.
- Ascensia (Contour). Ascensia’s CONTOUR NEXT ONE user guide (US, mg/dL) read. It has a coloured smartLIGHT at the strip port, apple meal markers (a crossed-out apple for fasting), and error codes E1 to E99 in three groups.
- Abbott (FreeStyle). The FreeStyle Freedom Lite owner’s booklet read, in its Australian edition, which prints every limit in both mg/dL and mmol/L. It is the oldest-style screen here: a thermometer, a battery, mem, davg for day averages and Error 1 to Error 4.
- GlucoRx. GlucoRx publishes its Nexus manuals on glucorx.co.uk, but the site refused our requests (HTTP 403) when we checked on 2026-09-28, so nothing on these pages is sourced to GlucoRx. If you own one, read the manual that came in the box.
- i-SENS (CareSens). We found CareSens manuals only on third-party manual sites, not on i-SENS’s own, so nothing here is sourced to CareSens.
Related pages
What these pages cannot do
- They do not identify a specific blood glucose meter model. They say what a symbol means on the makes cited (Abbott, Ascensia, LifeScan, Roche); your model’s manual gives the exact measuring range, unit, memory size and codes.
- They cannot tell you what a result means for your health or what to do about it. Every maker cited says to follow your healthcare professional; where a manual adds more, the page quotes it and names the maker.
- They do not cover continuous glucose monitors (CGM) or flash readers such as FreeStyle Libre, whose screens and alarms are different and have their own manuals.
- They cannot check your meter’s accuracy. The makers cited use control solution for that, and each prints the acceptable control range on the test strip vial or box, not in the manual.
- Left out: Ketone warning (KETONES? or a ketone symbol). None of the manuals we could read shows a ketone warning on the meter’s screen — the Contour Next One guide only lists the symptoms of ketoacidosis — so there is no page until the manuals of two different makers can be read and cited.
- Left out: Bedtime marker (a moon). Only the Accu-Chek Guide manual among those we read has a bedtime comment symbol, so there is no second maker yet.
- Left out: Event tags, patterns and awards (OneTouch Verio Reflect). Carbs, stress, illness, medication and exercise tags, Blood Sugar Mentor messages and gold, silver and bronze awards are one maker’s own features with their own drawings; no other manual read shares them.
- Left out: Bluetooth, sync and flight-mode icons. They say whether the meter is talking to a phone app and have nothing to do with the reading; each app’s own help explains them.
- Left out: Marks printed on the box, strip vial and meter back (IVD, LOT, use-by date, temperature limit, read the instructions). They are standard medical-packaging symbols from ISO 15223-1 that already have their own pages on this site, linked under Related pages above, so they are not repeated here.
Sources
Every document below is a maker’s own manual or support page, fetched and read on the date shown. Each symbol page quotes what its sources show.
- Roche: Accu-Chek Guide blood glucose meter — user manual (US, PDF) Checked 2026-09-28.
- Roche: Accu-Chek — Guide meter error codes (support pages for E-1 to E-14, HI, LO and the battery icon) Checked 2026-09-28.
- LifeScan: OneTouch Verio Flex — owner’s booklet (US, PDF) Checked 2026-09-28.
- LifeScan: OneTouch Verio Reflect — owner’s booklet (US, PDF) Checked 2026-09-28.
- Ascensia: CONTOUR NEXT ONE blood glucose monitoring system — user guide (US, PDF) Checked 2026-09-28.
- Abbott: FreeStyle Freedom Lite blood glucose monitoring system — owner’s booklet (Australia, ART22410-102 Rev. B, PDF) Checked 2026-09-28.