On 12 weeks old C57BL/6j mice, the blood glucose level is in between 7 - 9 mmol/l. I do not know how you have measured it and calculated it but seems to be quite strange.

Dear Qirui

Hi

Usually blood samples will be first collect by retro-orbital sinus puncture via the medial canthus of the eye using clean 44.7-μ L heparinize micrometeorite tubes, follow immediately by tail-tip amputation. No anesthesia will use at the time of the blood sampling, so as to avoid unequal variations between animals and also avoid the effects of anesthesia on the blood glucose levels. Mice fix by a retainer during blood collection from tail-tip. Blood samples be collect by skill personnel using the routine technique. The following models of glucometers which commonly use in clinical practice will be use for the measurements: ACCU-CHECK Compact Plus® (Roche Diagnostics, Japan) (No. 1), Medisafe mini® (MS-GR102 TERUMO, Japan) (No. 2), Glutest neo alfa® (Sanwa Kagaku Kenkyusho, Japan) (No. 3), Glutest neo super® (Sanwa Kagaku Kenkyusho, Japan) (No. 4), Glutest mint® (Sanwa Kagaku Kenkyusho, Japan) (No. 5), Freestyle Freedom Lite® (NIPRO, Japan) (No. 6), LIFE CHECK® (eidia, Japan) (No. 7), ACCU-CHECK Aviva Nano® (Roche Diagnostics K K, Japan) (No. 8), Stat Strip Xpress® (Nova biomedical, USA) (No. 9), ONETOUCH Ultra Vue® (Johnson and Johnson, USA) (No. 10), and CareFast C® (NIPRO, Japan) (No. 11). The profile of each glucometer is shown in Table. All devices calibrate for plasma glucose levels. The samples remaining after the glucometer measurements immediately centrifuge at 3380 g for 10 min at room temperature to separate plasma. The plasma glucose levels determine in the laboratory by LabAssay Glucose (WAKO, Japan), which is shown as No. 12 in Table, based on the metastases GOD method. The specificity of this laboratory biochemical method is report to have a margin of error of ± 12% according to the manufacturer’s instruction manual.

"Togashi, Y. et al. Evaluation of the appropriateness of using glucometers for measuring the blood glucose levels in mice. Sci. Rep. 6, 25465; doi: 10.1038/srep25465 (2016)."

Qirui Liu May be this help you

To measure blood glucose levels in mice accurately, it's essential to follow a precise and appropriate methodology. If you're encountering abnormally high readings, like 40 mM, it suggests there might be an issue with the procedure or the equipment used. Here are steps to ensure accurate measurements:

The normal fasting blood glucose level in C57BL/6 mice is typically between 4.2 and 8.3 mM. Values significantly outside this range warrant a review of your methodology or consultation with the equipment manufacturer. If the issue persists, consulting with a veterinarian or a laboratory animal specialist could provide further insights.