Carbs turn into sugar. When you eat a lot of either sugar, or foods that turn into sugar, you get a surge of insulin in your blood which binds to the sugar and brings it to the liver for storage. Sometimes there's so much insulin because of the surge, that it leaves your bloodstream depleted of sugar, and that's when you get the feeling of being low. It's better to regularly eat a good variety of foods including proteins/legumes, complex carbs (like vegetables and whole grains), eliminate sodas, and limit refined foods and simple sugars.
Diabetes occurs when either there isn't enough insulin or the insulin that you have isn't working efficiently. This makes your blood sugar high because the insulin can't bind to it and take it for storage. High sugar in the blood, over time, can cause problems throughout the body.
So we're really talking about two separate things. In the OP, you thought you might be low. Now, you've had a reading that was high, but we don't know when that was taken. When you last ate before the bloodwork would make a difference in how the reading is interepreted. The A1C will be important, too, because it will give an average of your readings over the last couple of months.
A dietician will review what I told you above (about carbs) and go over your current diet as it stands. Then she will show you how you should be eating, how to read labels, and make recommendations for a carb controlled diet for you. She will likely show you proper serving sizes of foods. For example, a serving of rice is 1/3 of a cup, which comes as a surprise to many. She will also talk about the role of exercise, and how it helps burn excess blood sugar. She will give you some teaching materials on this and also make another visit for follow up in a couple of months.
Whether or not you have diabetes will be determined by your doctor once all the results are in. It may be that you will be given a chance, if your blood sugars are shown to be on the high side (but not super high), to control them with diet and exercise. On follow up with your doctor (yes, you'll see her again lots) you will have repeat bloodwork to see how your average sugars have been again and whether you've achieved any weight loss, begun an exercise program, etc.
There's a lot to learn, but there's a lot of support available in the diabetic community also. Hope this helps, and good luck to you.