New & New to LCHF - Keto Flu?

Hi Kalkie and welcome to the forum.
You probably have no idea how high your Blood Glucose levels were before you started to change your way of eating.
If it was much higher than now (as it may well have been) then your body could be feeling unwell because it is not used to the healthy normal BG levels you are having now.
You have started hard and fast, which is the opposite to the way most people go about reducing carbs, your great BG readings are a testament to that. The downside of this is that the sudden change in what you are eating will naturally have an effect on your digestive system. The old carb loving microbiome will be dying off and being replace by microbes which prefer the food you are now n. This only takes a few days, but it is understandable if you have some digestive problems until things get back in balance.

So far as feeling cold is concerned, it may be that you are eating fewer calories than you did before. If this is the case then until your body adjusts to 'fat burning mode' your body will be in energy preservation mode making you more sluggish and thus feeling colder. What I did initially was to increase my intake of traditional fats to more than compensate for the reduction in carbs. Thus consuming more calories than before, until I got 'fat adapted'. In my case I was eating more eggs, cheese and avocados.

Getting 'fat adapted' often takes 2 weeks (more if the carbs are reduced slowly). You know you are fat adapted when you don't actually feel hungry at a normal mealtime. I found I was no longer hungry at breakfast time, so now I eat only 2 meals (sometimes only one) per day - lunch and dinner.

Having said all the above, it's possible that your symptoms are caused by an infection or by something else. Personally I doubt its an infection because infections tend to raise Blood Glucose significantly.

In general a LCHF way of eating will tend to reduce both weight and Blood Pressure (if its was high). Dr David Unwin a low carb GP found he started getting light headed when standing up quickly because he was already taking BP meds. So he de-proscribed himself the BP meds and his BP was then fine with the LCHF.

I don't think he was particularly overweight, so it seems that the effect on Blood Pressure is separate from the weight loss or the Blood Glucose improvement. He also says 'Don't blame salt for what sugar did' - meaning that is is commonly thought that people with high BP need to reduce salt in their diet. This doesn't always apply - particularly for people on LCHF because we tend to eat less salt than the average person because of eating little highly processed food..

On the Cholesterol situation, it is almost universal that LCHF increases HDL Cholesterol (thought to be good) and reduces Triglycerides which is also good. However in some (including me) it also increases LDL cholesterol which is required for making hormones, immune response etc and so isn't always as 'bad' as most people (including GPs ) think.