What questions should I ask

Well, they are still looking at the cause so I would guess that is positive news. Someone has already posted regarding Blood Pressure - a sudden drop can cause blackouts. Were you doing anything unusual? Has your routine changed? Is your diet balanced? Drinking enough water? It must be good news if they can't find anything wrong, so perhaps there is some action you could take to improve your overall heath?

Its a good idea to book an appointment with your GP now.
Write down your list of questions before you go so that you don't forget anything.
Ask about your blood test results and whether everything is normal.
The kidney function test had to be redone, so specifically ask about that.
Take your time and make sure your GP answers everything. Don't be rushed.
This should then give you an idea of where you stand.

I'm in a similar position at the moment, Nannyme.
Good advice to write down the questions as they come to mind.
Also take someone with you to write down the doctor's replies, as you will probably forget. Or get it wrong.
(If you're anything like me).

In any situation where I'm not sure, not just health I ask 'what are the questions I would have asked if I knew more about it'. Sometimes I get really helpful responses.

Nannyme, I don't suppose you want to know all the medical explanations . You may want to know the general cause such as a drop in blood pressure, or low blood sugar or whatever.

I guess that the main thing you want to know is what you or doctor should do to avoid this fainting happening again. The other thing you may want to ask is if the fainting is a sign of a really dangerous medical condition. Please don't be thinking that it is, but you very likely need to ask for reassurance.

I have had two collapsing episodes that are unexplained; both preceded by epigastric pain, and the last one lasting 45 minutes of unconsciousness.

I've had every investigation in the book and still none the wiser, but the fact that I have now started with AF makes them think it was probably to do with heart rhythm.

All I can do is keep my fingers crossed.

Maybe you could take someone with you to help in remembering what has been said? If you have a smartphone or iPad, download a recording app and ask if you can record the conversation with the doc.

I too am in the middle of "investigations".. Nannyme and found it very helpful to write all my symptoms down.. so did the doctor when I plonked the list in front of him.. he methodically went through everything and it was a great help, as A- I didn't forget anything, and B- I was feeling a bit emotional so didn't have to explain every little thing..
But don't we become aware of every little strange symptom when we are older?... things I wouldn't have even noticed in past years!.. I do hope you get sorted..things like that can be a bit scary even when they're not serious.. take care and good luck. ?

Another little piece of advice - when you book, ask for a double appointment - this ensures you don’t feel rushed and can fully take on board what you are being told. Otherwise, it feels rather like being on a conveyor belt ?. Hope everything goes well

Previous posters are right, all you can do is be prepared for your next appointment. Don't start letting your imagination run riot on 'what it might be', you have only had normal tests so far.
Questions to ask might be 'what is your differential diagnosis?' if you want to know what your doctor is considering, but bear in mind this will include the very unlikely problems as well as the likely ones.
If given a choice of options, the best question is 'if it was your wife/mother facing this, what would you recommend?
Ensure you get a copy of any referral letters so you are kept in the loop.
And write down a list of your worries. Doctors have no clairvoyant skills, so they can't reassure you or explain if they don't know what is causing you concern, which they will naturally want to do. Good luck, and give yourself some little treats and things to look forward to!

nannyme I am sorry you are not feeling 100% but hopefully the investigations will be able to put your mind at rest. I do think though if you are not feeling great it might be time to take stock of how you are taking care of yourself. The NHS Choices website has several different questions to answer re lifestyle choices. If you go through these you can see where they may be things you can do to give yourself a health boost. In the meantime treat yourself to something nice, try to get some rest and take care.

So that I can keep track of my health I pay for a health screening every 2 years by a firm that comes round. I then have a booklet with all my results shown as green, amber of red. And all explained. Some doctors do not approve of this approach but I am very happy to be able to take it to my GP and by appointment discuss the red flags and have things sorted.

I then keep files at home for every section of the test i.e. blood, blood pressure, eyes, knee etc. Whenever the GP has tests done or reports sent in she prints them off for me and they go in the relevant individual subject file. Then when I see the GP I take the comprehensive screening report with me and the previous print outs for the subject under consideration.

It does sound as though they are being very thorough which is encouraging. I've been a fainter my whole life so I do know how distressing it can be. But sometimes there is no obvious cause. So please try not to worry too much and wait until the next set of tests come back to rule out anything they need to fix.

Low blood sugar can cause this. You said you were in a public place, so perhaps you got too hot? You hadn't eaten enough? It was stuffy? Not enough fluid? You hadn't emptied your bowels properly which can cause fainting. Or even a virus.

If none of those things apply and you're feeling off colour you could be anaemic, lacking in something in your diet so generally run down.

I fainted as a child in assembly (more than once) on trains, in a queue at the chip shop! and even fainted once sitting in a seat at the cinema. I started to fit because instead of lying me on the floor, my sister tried to hold me upright. So if you fainted in a public place, did they put you flat or in the recovery position so you came round quicker or was someone holding your head up so oxygen couldn't reach your brain and it took longer for you to come round?

I understand your worry but I don't think there are questions really until the results are back and they should be asking you the above questions to rule out the above.

I do wish you well and hope it was a one off. These things do sometimes happen, especially as we age and need to take things a little easier. Oh, and take someone in with you. When you are worried it's so easy to freeze and not take information in. I think you need to get answers before you make questions in your case.

I can't really think of questions for you at the moment. It's answers from your test results that you're looking for. Should you get a diagnosis, that's when you need all the information and I would take someone with you to jot things down or sometimes a doctor will give you a print out of illnesses. I hope things go well and soon be feeling better.
flowers

Be straight with the professionals and tell them you want to know and understand what they are investigating and what the problem is(assuming it gets a definitive diagnosis). Make a note of all your questions and take them with, health professionals do appreciate that as it builds a relationship more effectively. Take someone with you too if you can

Ask your GP for an ECG just to rule anything out re. the heart. This can be carried out at the surgery by the practice nurse.

Nonnie, I think that is a really great question to ask in all sorts of situations. I try to inform myself as much as possible from numerous sources about any issue I am facing but have also found people generally respond very well to a question phrased like yours. Despite the gray haired little old lady appearance people do respond to an inquiring mind. Acknowledging that I am on 'a steep learning curve' about something usually elicits helpful responses. Those that don't respect that approach don't get my business again - if I have a choice, of course.

Gosh thank you all for such a great response, I have read through all your answers very carefully and it has really helped, so I will go armed with sensible questions written down so I don’t forget, which is highly likely, and an appropriate list of symptoms. Thank you all xxxx

Ask them to check for thyroid problems - I think kidney function tests would pick this up anyway. I have an under-active thyroid, diagnosed quite by chance, but now have medication. I'm still in the process of getting my head around it and the symptoms, but nonetheless I'm glad it was picked up - apparently quite common in women (especially) over 60 - I'm 65. Good luck and don't worry!

You have all been so helpful and tests are on going but still no positive answers but it seems to be honing in on my kidneys, so fingers crossed everything will be sorted soon.