If you use cinnamon for your diabetic disorder you have to follow 3 simple rules:
1. It must be cassia
2. It must be an extract where cumarine is removed during the process.
3. It must be a dosage beyond 3g daily intake.
For a safe extract of 10:1 it amounts to 300mg then.
You mustn't take regular cassia cinnamon as you will easily croos the threshold of daily cumarine intake. Ceylon cinnamon is delicous, but that's all you get then. To the contrary, cassia showed postive effects in decreasing HbA1c. Here, again, under certain conitions: it showed effects on HbA1c's that are beyond 7-8%. That means, well managed diabetics with HbA1c below 6% will be likely to not benefit. For those above 8%, studies showed a decrease up to 1% of HbA1c.
Cumarin is proven to cause (reversible) hepatic disorders. You don't want that, so go for safe extract if you want to give it a try