The short answer
- No universal code list: “E-4” on one brand and “ER4” on another can mean different things. The manual’s “error messages” page is the authority.
- Most common causes: not enough blood, blood added after the strip timed out, a used or damp strip, the strip removed during the test, or the meter too hot or cold.
- First fix: new strip from a closed vial, wash and dry hands, form a full round drop, apply promptly, keep the meter still until the result shows.
What meter errors usually point to
Manufacturers group errors into a few families. The numbers differ, but the fixes are similar.
| Family |
What the meter detected |
What to do |
| Sample errors |
Too little blood, blood applied too late, sample applied twice, or blood on the wrong part of the strip |
New strip; bigger drop; touch the drop to the strip’s edge or tip as the manual shows; don’t add more blood to the same strip |
| Strip errors |
Strip used, wet, damaged, expired, inserted wrongly or the wrong type for this meter |
New strip from a vial that has been kept closed; check expiry and the “discard after opening” date |
| Strip removed early |
Strip moved or pulled out during the countdown |
Retest and keep the meter still |
| Temperature |
Meter or strips outside operating range (often about 10–40 °C) |
Leave both at room temperature for 20–30 minutes, then retest |
| Meter/electronic faults |
Internal fault, low battery, damaged port |
Change the battery; if the error persists, call the helpline (number on the back of the meter) |
| HI / LO |
Glucose above or below the meter’s range (often >33.3 or <1.1 mmol/L; >600 or <20 mg/dL) |
Retest immediately; act on it if confirmed (see below) |
HI or LO is not a fault code. If a retest confirms “LO”, treat for hypoglycaemia at once (15 g fast-acting glucose, recheck in 15 minutes). If it confirms “HI”, check ketones if you can and contact your diabetes team or emergency services, especially with vomiting, abdominal pain, fast breathing or drowsiness.
A step-by-step retest
- Wash hands in warm water and dry them completely (sugar on fingers, hand cream and wet skin all cause errors or false readings).
- Take a new strip, close the vial straight away, and insert the strip fully the right way round.
- Wait for the “apply blood” symbol.
- Lance the side of a fingertip; let a full, round drop form without squeezing hard.
- Touch the drop to the strip’s sampling edge and let it draw the blood in until the meter beeps.
- Keep the meter flat and still until the result appears.
If the same error appears with two or three fresh strips, run a control-solution test. If that also fails, the meter or strip batch is likely faulty: contact the manufacturer, who usually replace meters free of charge.
When readings don’t match how you feel
Even without an error message, a reading can be wrong. Under the ISO 15197:2013 standard, a meter may read up to 15% above or below the lab value (above 5.6 mmol/L or 100 mg/dL) and still pass. Readings can also be affected by low red-cell counts (anaemia) or high counts, dehydration, very high vitamin C doses with some strips, and testing on alternate sites while glucose is changing. If a result doesn’t fit your symptoms, wash your hands and retest from a fingertip. More on testing accurately is in the diabetes care guide.
Frequently asked questions
What does E-4 mean on an On Call meter?
On Call models differ, so check the error table in your model’s manual or the ACON/On Call support site. In general, codes in this range are sample or strip problems; retest with a new strip and a larger drop.
What does E04 mean on my glucose meter?
On several brands, E04-type codes indicate a sample or strip problem (for example too little blood or a used strip). Because meanings vary, confirm with your meter’s manual.
Can I reuse a strip after an error?
No. Strips are single-use; once blood or moisture has touched one, use a new strip.
Do cold strips cause errors?
Yes. Strips and meters left in a cold car or near an air conditioner often give temperature errors. Let them warm to room temperature first.
Date, time and memory resets are covered in how to reset a glucose meter.
Sources and further reading
CanforaMedicine Guide
