Yes, though depending on what your diagnosis is, you may be able to get a monitor which allows you to track your blood sugar in near-realtime. The technology has advanced a lot in the last 20 years.
perhaps occasional bouts of keto can be therapeutic?
Popular brands of it in the US are Freestyle Libre and Dexcom.
Their final cost to you will vary hugely by your insurance provider. Some with little to no cost, and others several dollars per day.
If you like data and are analytical by nature, and since you’re on HN that’s fairly likely, I’d highly recommend using them for a little while if you can afford it. They’re great for newly diagnosed people to understand in near real time without repeated finger pricking. But those are no terrible either and much better than not managing and monitoring! Slightly annoying at first but it is something that most people can get used to fairly easily.
You're not measuring HbA1C in real-time; you're measuring the blood sugar in real-time.
HbA1C is a lagging indicator, used because it's a convenient and non-invasive diagnostic and a summary statistic. It's not the way you measure the short-term or medium-term effectiveness of interventions.
I do wonder if A1C remains a useful metric though, as perhaps it better captures the actual damage done by consistently high blood glucose. Would be interesting to see if there is research showing that CGM area under the curve is a better (or worse) predictor of clinical outcomes than A1C.
Both metrics have their own use. Continuous glucose monitoring is better for measuring the short-term impact of interventions, but it's also more invasive (albeit less so than it used to be) and more expensive. HbA1C is still measured for diabetic patients who have continuous glucose monitoring.
One downside of A1C is that the baseline values actually vary, and it's known to be either downward biased or a particularly lagging indicator for certain groups that are predisposed to Type 2 diabetes (e.g. South Asians and people of African descent).