I lied at MEPS. Will they go back and look through my medical records?

They can only look at your records if you sign a release form. Otherwise, HIPAA protects this information. But, yeah. Why are you posting this here?

Listen to your recruiter.

Wow! I’m to trust you in a foxhole? My nephew lied, they found out and he was discharged

Best for you is to tell recruiter you are not fix for duty. You said the MEPS Dr. Discovered the murmur also. You should consider your health and safety and the other lives you can endanger

Tell the truth even if it goes against you. The only thing that you truly own is your integrity, once you lie, that stain will follow you. Tell them and tell them why you lied. They may accept your answer and allow you to continue. Worse case is that they cancel your contract since you haven't been sworn in and shipped off to boot camp.
But be a man and own it!

John, first... heart murmur. Never good as it means your heart valve(s) is/are not working as designed. Depending on how bad it is could be a serious issue when under duress, either in training or actual combat. Worse case... death. Best case... feeling much more tired than your peers after a workout. Usually the government would not want to take the risk that something would happen to you.

Second... lying. We all make mistakes when we’re young. That said... this is your health and future we’re talking about. Man up. Take responsibility. Whatever the outcome it will help you grow if you’re open to learning from your mistakes. DO NOT try to hide this further or act dumb! That would be another serious mistake.

More than likely you will be found out you lied. NEVER admit that you lied on social media that was plan stupid. What the hell were you thinking?

So, no. MEPS doesnt have access to anyone's medical records, they are protected under the hipp act. However, they can see posts on public forums, kinda like this one...

It is never a good idea to Lie about anything especially dealing with the Government. Having said that, you were told that you would outgrow the heart murmur. In my 15 plus years of recruiting, this medical condition comes up on occasion. The majority of applicants that go to MEPS fill out the medical paperwork and do not disclose this condition because he/she think they outgrew this condition.
Keep in mind, your recruiter and Station Commander should have questioned you for any medical issues that you have now, or in the past . Recruiters and Station Commanders worth their salt always get to the bottom of things, ESPECIALLY Medical issues !!!
You probably have been put in for what's called a "Med Read". This is a Company level Med waiver that the Captain/Major will initiate (unless things have changed a bit since I retired). The applicant (YOU) should write a signed statement to the Commander as to the nature of the medical situation and your reasoning why you did not mention the heart murmur in the first place. In your case, you felt that you outgrew the heart murmur etc...
Social media is great! But there is a time and place to communicate things. This is a private medical issue and you should refrain from social media feedback. Get with your recruiting team to discuss this. Believe me, the Recruiting team want to put you in boots!

It confuses me to hear someone say they "lied" but then told "a bunch of others". The purpose of telling a lie is to hide something. Doesn't going around telling a bunch of others, including how many on this site, that you lied defeat the purpose? Now everybody knows you lied. Not very smart of you!