Hi, I have been doing Keto for nearly four years.
What you are reading is relatively normal blood glucose levels.
They can range from about 3.5 to 6.00 mmols.
The idea of being in ketosis is to keep your blood levels in as close to normal range, to maintain stability, to give your body, the relief from having an imbalance in your hormonal response to food. Namely glucose and insulin!
No high spikes, no imbalance.
Finding your balance of protein, fats and how much carbs you can tolerate is important to being in ketosis.
Best wishes