In Ontario, there's a list of conditions where a doctor is legally required to report you to the Ministry of Transportation. Issues with alcohol are one of those. It's quite common for an individual to go to a clinic or hospital for alcohol related issues and find they've been reported to the ministry.
Can you appeal? Yes, you have to file an appeal with the License Appeal Tribunal.
A lot of people tend to get confused with the idea of an appeal. They are very strict about what is and isn't considered relevant. From the Tribunal:
In most cases, the best evidence will be reports from doctors or other medical professionals. When you appeal, it is actually the Ministry that is required to prove that your licence should remain suspended or downgraded. You should know that they have at least one report they can enter as evidence – this is the medical report which resulted in the suspension or downgrade of your licence. To argue against the report in the Ministry's files you may wish to file a medical report that makes different findings.
In an appeal, the Ministry is required to prove two things:
1) that you have either a mental, emotional, nervous or physical condition or disability, or an addiction to the use of alcohol or a drug; and,
2) that this condition, disability or addiction is likely to significantly interfere with your ability to drive safely.
The legal test for your appeal is all about the reported condition, disability or addiction, and how that affects your ability to drive a motor vehicle safely. Your evidence must be relevant to that legal test. Other evidence, such as how much you need your licence for work, or other reasons, will not help you in your appeal because that evidence does not say anything about the reported condition or whether your condition is likely to affect your ability to drive safely.
A successful appeal would rely on evidence from a doctor or medical professional.