Definitely keep record of all this, if it comes down to disciplinary procedures against you then they will certainly be documenting everything. I had this problem with return to work meetings after non-diabetic related periods of sickness.
Totally famalirise yourself with the works sickness, disability and suitable adjustments policies. You are covered by the human rights act and the dissabilities discrimination act. All this can be taken to support you with your discussions with HR and support/assessment from Occ health.
Your health is paramount and if they wish you to perform then they need to take your needs into consideration, they are legally required to do so.
You are being discriminated against, you require breaks to facilitate the management of your condition, be they used for testing, taking shots or having something to eat.
I managed the turn the tables on the managers who were found deficient in having delt with me fairly according to policies. My disciplinary was quashed, Occ. Health advised additional breaks and allowances with regards diabetic related sickness absences.
Don't let them bully you, having hypos and making you feel sick/bad is totally unacceptable. Good luck.
Regards ash