@Little chef are you testing your tolerance to different foods.
Generally, when we have diabetes our bodies are not able to tolerate carbohydrates.
However, the amount of carbs we can tolerate varies a lot between us.
So, frequent advice is to test before easting and then 2 hours after. If your blood sugars rise more than 2mmol/l between the readings, it is likely that you can not tolerate the food you have eaten. When first diagnosed, it is a good idea to keep a note of teh affect different foods have on your blood sugars in this way and adapt your diet accordingly.
As other have stated, weetabix are high in carbs, therefore, many people with diabetes find that they are unable to tolerate them.
The other thing to consider in the morning is Dawn Phenomenon and/or Foot on the Floor. THis is where our livers helpfully flood our body with glucose at the start of the day to give us energy to get moving. Due to this, it is common that people with diabetes are able to tolerate less carbs first thing in the day.