Can I cut 10 mg amlodipine that was prescibed in half to 5 mg because of side effect?

My cardiologist told me to cut my pill in half and start taking 5mg instead of 10.
It's been a few weeks since I've done that and all is well.

It will depend on whether your tablet has a special coating or not.
If it has a special coating then it should not be cut in half.
Your pharmacist will be able to help you.
Have you talked to your doctor about the side effects you are experiencing?
You really should not reduce your dose without your doctors approval.