NB - do you mean summer 2025? For 2026 entry? I have written the following based on that 😁
No. It won't hurt it. But you might want to consider if it is the best tactic for you.
You may well have very good reasons why you don't want to apply in year 13 and that is an important factor in your personal decision.
This is a long one, so apologies in advance...
1) a significant proportion of people take more than one admissions cycle to gain an offer. Sometimes 3.
This will mean possibly 2 gap years. Or even 3. If so, there will be a strong expectation I would have thought, that you had furthered your application through relevant work in the interim.
2) the year in which you apply is full on. UCAT in the summer previous, then Personal Statement, then submitting your application. (Who will be your referee if you are in gap /2nd gap year?), then possibly next stages of applications (supplementary forms /tests) and answering any med school inquiries needed - then a good couple of months of interview prep and interviews, and these dates could all be done by December even or go on to April. It depends on where you apply and how they handle your application. Then offer holder days etc. Then sorting out anything that needs to be done for hour offer and accommodation etc.
So it's a lot. It's timing is also unpredictable. So you won't be able to wander off travelling or anything or if so, only within a very short time frame whoch you may not be able to plan too far in advance. Have you got somebody (other than TSR 😉) to support you through this? There is something about doing this in year 13 with teacher and friend support and others going through the same thing at the same which can be very reassuring.
However. It is a lot to do in year 13 (and you will have needed to get some.work experience etc before submitting your application). And it is a lot to do alongside your A levels and still get those all important grades. So it is woth considering if it will be too much.
3) if you don't intend to do any relevant work experience during your gap year then I am sure that there will be good things you can draw on but you will still need to do something medicine or care related / and possibly dependant on what you are doing at the end of year 12 start year 13. Some med schools will specifically disregard medical health experience gained overseas unless you are a resident of that country, so won't be able to pick it up formally elsewhere. And it can take a while to source and organise.
3) UCAT. It can be a bit of a beast and people who were going along brilliantly in prep can have a shocker. Or visa versa. People often find they do significantly better second time around.
You may not have a choice in all this, you might have particular circumstances that mean you have to take a gap year and then apply. That is fine and perfectly achievable, but be aware of the potential complications I've listed above and plan them through for you, and there is lots of support on TSR if you need anything as you work it through.
But, if this is a choice thing, then my suggestion (which would take a bit of effort) would be:-
> Press on with BSMS online, observe GP and arranging relevant work experience in year 12. You will need it whenever you apply.
> if you can, do a lot of revision for UCAT this summer and take the test this year.
> once you have your UCAT score then that might help you make a strategic decision about whether or not you might wish to / are able to apply for a deferred place for 2026. If you take your UCAT earlier in the summer it gives you a bit more time to work out your options to make a strategic deferred decision. Work backwards from your school's early entry deadline to think about what you might need to do.
So this would mean that you could apply in year 13 and have the school support and if you get a place for 2026 then the place is yours if you get the grades, and you can go off and do whatever you want whenever you want during your gap year.
If you aren't successful in that cycle (and many aren't first time around) then at least when you do it again in your gap year, you have the experience and knowledge to do it easier on your own. In many cases a second go at UCAT will also improve your score and open more doors.
You will also have a better understanding of application workload and thus will be able to better plan your gap year.
If for whatever reason you have a disastrous UCAT this summer then you may decide its not worth pushing forward, and then just apply in your gap year as per your previous plan, and given UCAT often is better second sitting then its not totally wasted effort.
Sorry for the long ramble but hopefully some food for thought.
Others with more experience will no doubt have different advice and views.
The great thing about advice, you don't have to take it, but hopefully between us we can help you make an informed decision.
Good luck whatever you decide.