How to Diagnose Yourself Using the Internet in 4 Steps

Despite the fact that most experts will tell you not to attempt to diagnose yourself using the internet, we do it all the same. Therefore it makes far more sense to approach your self-diagnosing in a measured way, providing a better chance that you'll come up with the right answer and will eventually get the right treatment.

If you've decided you want to diagnose yourself, then your reason may be one of the following:

  • You may be trying to avoid seeing a doctor until you know you really need to see a doctor.
  • You may be fearful of what your symptoms suggest and want a better handle on the possibilities before you see your doctor.
  • You may have already visited your doctor but you have some reason to believe her suggestions are incorrect or need refinement.

Before You Get Started in Diagnosing Yourself

Whatever your reason for wanting to diagnose yourself, there are a few points to consider before you get started:

  1. I am alive today because I used the internet to explore and determine my diagnosis. Had I not dissected everything I knew about my medical condition, eventually realizing the diagnosis I was given was wrong, I might have undergone needless chemotherapy. Therefore, I am a firm believer that arming yourself with as much knowledge about your diagnosis as possible is an important part of your medical journey.
  2. No matter how successful you are in determining your diagnosis using the Internet, the library, or any other method, you must still collaborate with a medical professional (your doctor, nurse practitioner or physician's assistant). You may be trying to avoid your doctor, but only your doctor can help to confirm or refute your findings, and/or prescribe medical treatment.
  3. In this brave new world of self-diagnosis, be aware that you may be putting yourself at risk in at least three ways:​
    • If you are wrong, and you choose to postpone seeing your doctor, your mistake may cost your life or quality-of-life saving time or treatment or both.
    • If you depend on unreliable or non-credible websites to help you determine your diagnosis, you may be putting life and limb in jeopardy.
    • If you use your knowledge to make your doctor angry, he or she may be unwilling to work with you.

With those thoughts in mind, here are the steps to take to diagnose yourself using the Internet:

Step 1: Understand the Goal of Developing Your Differential Diagnosis

Differential diagnosis is a process of elimination. It begins with a master list of possible diagnoses that could cause a symptom, and then, by eliminating them one-by-one, narrows the list down to one cause - your diagnosis.

Doctors usually use the process of differential diagnosis to figure out what their patients' diagnoses are unless they think the source of symptoms is obvious (and therefore they think they don't need to use the process).

Obvious diagnoses might be flu symptoms in the middle of flu season, a rash developed shortly after a hike through poison ivy laden woods, or diabetes diagnosed as a result of consistently too high blood glucose levels.

But sometimes "obvious" isn't the right answer. There may be other reasons someone has flu symptoms in the middle of flu season, or a rash, or a high blood glucose level. Some medical professionals call this the difference between horses and zebras. It's those non-obvious diagnoses that should command the more exhaustive process of differential diagnosis. So if the doctor hasn't worked through the process, you may want to do so yourself.​

Making Your Own Differential Diagnosis

Your self-diagnosing should follow the same differential diagnosis process that your doctor would use. Especially in a case where you don't believe the doctor's diagnosis was correct, the differential diagnosis process will either give you more confidence in her verdict or will suggest you other, possibly more accurate possibilities.

Diagnosing yourself using this approach will do two things: you'll learn a great deal about what differentiates one possibility from another, and then later when you have the conversation with your doctor, you will feel far more informed and less intimidated than you might otherwise feel.

Step 2: Make Your List of Diagnosis Possibilities

Begin with the development of a master list of possible diagnoses. Such a list can maximize your chances of arriving at the right conclusion through your "differential" process of elimination. Your goal is to list as many potential diagnoses as possible.

If you have already visited your doctor, then hopefully you will have already asked her, "What else can it be?" Try to remember, then write down her diagnosis, plus all those other possibilities she mentioned. That's a start.

Whether or not you visited a doctor already, there are four websites that can help you develop your master list of possibilities. In developing your differential diagnosis, you'll want to use at least two of them, and possibly all four.

1. The Isabel Diagnosis System:

The Isabel Diagnosis System was first developed in 2006 by a father who almost lost his young daughter to a misdiagnosis. Today it is used globally by large health systems and diagnosticians who appreciate its deeper dive into possibilities. In 2012, a patient-friendly version of the Isabel system was launched. By simply inputting your symptoms one-by-one, it will help you come up with that master list of possibilities which you can then explore further.

• Link to the Isabel System website to make your differential diagnosis master list. This system for patients is free.

2. Symcat:

Developed by medical students at Johns Hopkins, Symcat (which stands for Symptom-based, Computer Assisted Triage) begins with a big disclaimer that it should NOT be used to diagnose yourself. What it does do is provide you with a list of possibilities based on the data it has collected from hundreds of thousands of other patients, data obtained from the CDC and other resources.

• Link to Symcat to make your differential diagnosis master list. Use of Symcat is free.

3. Right Diagnosis:

(Side note: back when I was exploring my odd symptoms in 2004, this website was already in existence, but it was called Wrong Diagnosis. When you link to it, you'll see the "WD" logo in the upper left corner, despite its name change.)

While Right Diagnosis isn't as patient-user friendly as the other two, it has far more exhaustive lists of alternative diagnoses. It may be helpful if you are trying to expand your master list of possibilities, especially if you are working through this process because you have been previously undiagnosed.

• Link to Right Diagnosis to make your differential diagnosis master list. There is no cost to using Right Diagnosis.

4. Up to Date:

Up to Date is a go-to, subscriber resource used by physicians all over the English speaking world which is kept (yes, you guessed it) up-to-date on a regular basis. The details of thousands of symptoms, diseases and conditions, treatments and their evidence are available to those physician subscribers, many of whom rely on that information everyday (like those who subscribe to Isabel.)

Keeping in mind that the material is written for professionals (and not for patients), savvier patients may still want to access Up to Date when they are ready to tackle more difficult information about their diagnosis or treatment options.

There are three ways patients can access Up to Date. They can simply type a question and get an answer for free. That, however, isn't particularly useful when working on a differential diagnosis. So, instead, patients can subscribe for one week or one month (about $20 or $45 respectively). Or, if their doctor uses Up to Date, they can ask the doctor to give them a 30-day subscription for free. Not all doctors who subscribe to Up to Date realize they have that capability - but it doesn't hurt to ask.​

• Link to Up to Date to make your differential diagnosis master list.

There are many other symptom checkers online. They are not nearly as robust as the ones mentioned here. If you are curious, you can find a list of additional symptom checkers and the reasons they may not be helpful.


A word here about cyberchondria; that is, the tendency for us to think the worst based on the information we find online. Just like the one extreme where doctors assume a diagnosis is not unusual, the other extreme is a patient thing - the tendency to overstate or to jump to wrong, very frightening conclusions about their symptoms. It's important to be balanced in your assessment.

Step 3: Use the Process of Elimination to Narrow Your Diagnosis List

Begin using the websites listed in the previous step, plus additional credible and reliable resources to help you narrow down the possibilities.

The Isabel system, in particular, will lead you to further information, photos, and resources for helping you either embrace ​or eliminate those possible diagnoses from your master list. Just be sure that any references you rely on are credible and reliable, and don't try to influence you to embrace any specific answer they can profit from. (e.g. a pharmaceutical company website that hopes you'll ask your doctor for a specific drug they manufacture.)

Your process of elimination will be your own differential diagnosis. As you work through it, make notes for yourself. They will help you in your discussions with your doctor when the time comes. You'll want to include the following:

  • Why something does seem to "fit" your symptoms and circumstances
  • Why you think a possibility doesn't fit or isn't relevant
  • What else needs to happen to explore a possibility further? For example, if you'll need a certain test, or you need to wait to see if the next symptom develops, or if you may have a symptom you aren't aware of (e.g. you may not know if your blood pressure is high or low or whether a certain disease is in your family history)
  • Questions that still need to be answered
  • Links that you may want to return to later

You may arrive at one answer that is most probable, or a handful of possibilities may still remain. This is one reason why you'll want to do this in partnership with your doctor since he can order the right tests, or make further suggestions for you.

Step 4: Visit Your Doctor to Complete the Diagnosis Process

As mentioned at the beginning of this article, whether or not you are able to diagnose yourself using the web, you will still need to coordinate with your doctor.

By now you have narrowed down your list of possible diagnoses and you will either have a good idea of what your diagnosis is, and/or you will have a list of questions or testing needs to discuss with your doctor.

Be aware that there are the right ways and the wrong ways to approach your doctor with what you already know. How you handle your visit and discussion with your doctor will be critical to your successful diagnosing process. It's all about respect and not stepping on toes. Be sure you approach your doctor the right way.

There are only three possible outcomes from your conversation. Either you will both agree, or you will disagree and need to look further, or your doctor will decide she doesn't want to participate in the conversation with you about alternative diagnoses (in which case, you'll need to find a new doctor).

If the two of you agree, then whether or not you choose to get another opinion will be optional since your research produced your first opinion, and your doctor produced the second - or vice versa. Regardless of whether or not you agree, there are times when it only makes sense to get a second opinion anyway. Don't forget that caveat from the beginning of this article: any mistake can cost you life or quality-of-life saving time or treatment or both.

No matter how diligent you've been about working through your differential diagnosis, you may still be undiagnosed. If so, here are some steps you can take to solve your mystery diagnosis.