Hi and welcome to mm
Don't spend money on having tests. Your GP can run a blood test to check for things like iron, B12, vitamin D defiency etc if it's needed.
Are you feeling tired and run down?
It is important to have a good diet but when meno hits then one does need to focus a bit more to ensure you are getting enough of the right things. Cutting out as much sugar and saturated fats as possible is very important .
If like me you have a sensitive digestive system ( I'm also quite a fussy eater) and perhaps don't eat all the right things, then simply taking a good multi vitamin wont do any harm. My brother-in-law is a gastroenterologist and insists we all take vitamin D, especially through the winter months, as this is vital for many things and the main source of vitamin D is sunshine which few of us get enough of.
I also take Omega 3, although if you have oily fish 2-3 times a week you are possibly getting enough.
As I'm vegetarian I do take Feraglobin every day to ensure I get enough iron and B12.
Here are only a few vitamins you can OD on like vitamin A but our bodies will excrete anything we don't need from Vitamin supplements.
Eat plenty of vegetables, especially if they are green, fruit, eggs and fish with some dairy like a small chunk of cheese for the calcium. Eat plenty of fibre like whole grain cereals. Eat some cashew nuts and a banana for your snacks and go for good brisk walks each day. Take a few supplements ‘just in case' if you want. My theory is that our digestive system is less efficient as we age and the lack of oestrogen lowers our immune system, so boosting everything with some supplements may help.
Vitamin D and magnesium are well worth taking ( helps to absorb that calcium for our bones and boosts the immune system) and possibly add in calcium and Omega 3 for good measure BUT none of this can replace eating well.
There are plenty of good sites that offer advice on diet - do look at the sites like NHS Choises and not any site selling supplements.
The fact you are thinking about this shows you are wanting to do the right thing, so follow your instincts, get clued up on what foods you should be eating and then relax and enjoy life. DG x