Going to start with your questions from the bottom up if you don't mind....
Finally, I’ve been counting carbs and advised to start a ratio of 1:10 but this isn’t working. Say 30g carbs and 3 units but sugars going up to around 14? Is 2:10 ok for some people."
Novo(not so 🙄)Rapid works over 4-5 hours, so you are looking for it to bring you back down into range by your next meal. As long as it does that, the dose was correct so your 1:10 ratio is right. How high it spikes in between is usually down to timing.... ie how long you wait after injecting before eating otherwise known as the prebolus time. This varies from one person to another and at different times of day and with different insulins. Typically they suggest injecting 10 of maybe 20 mins before eating but that is just a general guideline. If you have a fast digestion and/or a slow response to the insulin, then you will need longer. If you have slow digestion or fast absorption of insulin then you will need less. How much more or less is down to careful experimentation.
For example when I was first diagnosed I spiked up to mid teens every morning with 20 mins prebolus timing but came back down into range before lunch, so the dose was right but the timing wrong. I gradually increased it by 5mins each day keeping my breakfast the same until I found a timing where it stopped the spike but didn't cause me to hypo. For me with Novo(not-so)Rapid, I needed about 75 mins between injecting and eating my breakfast. Obviously this is impractical and a few times I got distracted and left the house without having breakfast only to find myself having a massive hypo not long after. I ended up changing to Fiasp which is faster but I still need 30-45 mins prebolus at breakfast and I usually inject before I get out of bed because I have a very strong Foot on the Floor liver response(like Dawn Phenomenon) which will take me into double figures if I don't jab insulin before I swing my legs out of bed. Many other people would hypo waiting so long, so it is important to increase the timing gradually to see what works for you. I only needed 20-30 mins at other times of day with NR and just 10-20 mins with Fiasp. Breakfast tends to be the longest prebolus timing for most people.
What I am saying is that your 1:10 ratio might be fine but you are just not giving it enough of a head start. If however, the 1:10 doesn't bring you back into range 4 hours later, then you need to think about adjusting the ratio, but small adjustments are best and always err on the side of caution with insulin.
"Also, if your sugar is low ie 3.5 is it safe to take it before dinner?"
If it is confirmed low with a finger prick, then it is important to treat the hypo (with fast acting carbs) and wait until you are confirmed above 4.before you inject your insulin. At low BG levels you can become more sensitive to insulin which means that it can kick in much quicker than it normally does, so injecting when you are already hypo is potentially dangerous.
"If you don’t really eat lunch (say fruit or a yoghurt) do you still need to take it to get it in your system, even if sugars are in range?"
If you are only having a light lunch then it is much more important to carb count and only inject as much as you need. An apple or a yoghurt might only be 10-20g carbs so if you are in range and you inject 10 units with a 1:10 ratio, then you are almost certainly going to end up hypo. Fixed doses of insulin are supposed to be accompanied by roughly similar sized meals in terms of carbs, so if you were to have an omelette which has almost no carbs, then you would not inject for it. Similarly, if you were going to skip lunch, you would not inject. Unfortunately nurses rarely seem to advise people about roughly how many carbs they should aim for when they give people fixed doses, but if they have suggested 1:10 and to inject 10units, then they are expecting you to eat about 100g carbs per meal..... which seems like quite a lot to me. I think I was started on 4units per meal, but perhaps they have done a rough body weight calculation which suggests 30 units a day would be about right.
Hopefully that answers your questions but if you don't understand anything just ask.
