Control solution mark (bottle or C)
This result is a control solution test — a check that the meter and strips work together — not a blood glucose result. Marked results are kept out of your averages.
Check your meter’s manual — makers differ.
What it is for
Compare the number with the control range printed on your test strip vial or box, not with your own target range. If it is outside that range, the Accu-Chek (Roche), Contour (Ascensia) and FreeStyle (Abbott) manuals all say not to use the meter for blood glucose tests until the problem is solved.
These pages report what each maker’s manual says and quote it wherever health is involved. They do not diagnose anything, they are not medical advice, and they never tell you how to treat a result; only your own meter’s manual and your healthcare team can do that for your model.
- What it looks like
- A small bottle or vial beside the result — on the Accu-Chek Guide with a C on it — or, on the OneTouch Verio Flex, a C in a filled circle.
- Names makers use
- Control Solution Test Result Symbol (FreeStyle); Control bottle (Accu-Chek); Control solution result (Contour, OneTouch Verio Reflect); Control Solution (OneTouch Verio Flex)
Where makes differ
Who marks it differs, and that matters for your averages. Contour (Ascensia): “The meter automatically marks the result as a control test.” Accu-Chek (Roche): the meter shows Control Result and the bottle by itself, then a tick if within range or a cross if not. OneTouch Verio Reflect (LifeScan): you must choose Control Test from the Settings Menu first, and if the mark “does not appear on the screen, this result will be included in your averages”. FreeStyle Freedom Lite (Abbott): you mark it yourself by holding the c button for two seconds after the result.
What it does not mean
The control range is not a target for your blood: Abbott’s booklet says “It is not a target range for your blood glucose level”, and Ascensia’s says not to calibrate a CGM or calculate a bolus from a control result. It is not the IVD mark on the box.
Sources
No published standard we could check defines blood glucose meter control icons, so this meaning is taken from 4 makers’ own manuals and support pages, each fetched and read on the date shown:
- Ascensia: CONTOUR NEXT ONE blood glucose monitoring system — user guide (US, PDF) — Symbol table: “Control solution result”; Control Solution Testing: “The meter automatically marks the result as a control test. Control test results are not included in your meter Logbook, in blood glucose averages”; “Do not calibrate your continuous glucose monitoring device from the control result.” Checked 2026-09-28.
- Roche: Accu-Chek Guide blood glucose meter — user manual (US, PDF) — Symbol list: Control bottle, Checkmark / Control test OK, Control test not OK; Control Tests: “Control Result and the control bottle symbol appear”; “Control results are not included in the averages or blood glucose reports.” Checked 2026-09-28.
- LifeScan: OneTouch Verio Reflect — owner’s booklet (US, PDF) — Other meter icons: Control solution result; “Make sure you select Control Test from the Settings Menu before you begin a control solution test … If [the mark] does not appear on the screen, this result will be included in your averages”. Checked 2026-09-28.
- LifeScan: OneTouch Verio Flex — owner’s booklet (US, PDF) — Meter symbols and icons: Control Solution (a C in a filled circle). Checked 2026-09-28.
- Abbott: FreeStyle Freedom Lite blood glucose monitoring system — owner’s booklet (Australia, ART22410-102 Rev. B, PDF) — “To mark the result as a control solution result, press and hold the “c” button for two seconds until the control solution symbol appears”; “The control solution range is a target range for control solution only. It is not a target range for your blood glucose level.” Checked 2026-09-28.
Written in our own words; quotations are the makers’ wording.