Remember, going onto medication does not need to be a one way road, if you can control your blood sugars yourself and show that the levels are coming down you can always come off the injections later.
From the figures you have given your levels do seem a rather high, but without know for certain what test it was and what the measurement units were it, we may be misunderstanding it. So my advise is get the print out from your doctors if possible and let us know more details. Start home testing again (I notice you mention that you have done it before but not for a while, so I assume you have a meter) before you eat and 2 hours afterwards and what you ate for that meal. Hopefully then we can give you some pointers as to how you can reduce your blood sugar through diet as well.
You may not agree with the nurse, but rather than making a big scene and getting a bad note on your record it is sometimes simpler to just prove them wrong. You might also want to keep quiet about self testing and low carbing a lot of doctors and nurses don't seem to approve of it.
Just be warned, we are all different and treat our condition slightly differently, you ask 10 people on the forum for advise and you are likely to get 11 options of what to do, but most tend to go along similar routes.
