how many times a year can health insurance be raised?

my company just raised health insurance less than 6 months ago and are now raising it again is this legal
--------------------
If you buy your policy directly, your health insurance company can only raise your rate on the annual anniversary date. If you get it through your employer, your employer can switch policies every month if they want to, and can continually change exactly how much they contribute towards the coverage, thus increasing your cost every month, if it works out that way. So it depends on if it's YOUR policy, or your EMPLOYER'S policy.
Source