It's common to hear a Social Security disability (SSD) or SSI disability claimant state that their personal physician is "100% behind getting my disability benefits," only to later discover that the claimant's treating physician was not particularly helpful, or, worse, not supportive at all. This often comes to light as a disability applicant, or usually an applicant's disability lawyer or nonlawyer representative, is preparing a case for a hearing to be held before an administrative law judge (ALJ). At that point, you or your attorney should try to gather recent medical records as well as a supportive statement (that is, a medical source statement, or RFC form).
The applicant may find that the doctor's office is somewhat unresponsive to requests for medical records and that the doctor is unwilling to complete a lengthy RFC form. Why do doctors tell their patients that they support a patient's case for Social Security disability or SSI and then later, when their help is needed, become unreachable? In some cases, it may be that the doctor does not consider the patient to be disabled at all, regardless of whatever statements they have made to the contrary (doctors may say one thing to a patient's face and something else in their medical records). In other cases, the doctor may run an especially busy practice and may not wish to devote a portion of their time to a Social Security disability or SSI claimant's case. In this case, the doctor may charge a fee to fill out an RFC form. This money is money well spent, if you don't have an attorney who will pay for it.
But if your doctor doesn't seem willing to fill out the form, even if you pay a fee, you should consider switching to a doctor who does. In some cases, this may mean finding a physician with a smaller practice who is willing to devote more one-to-one time to patients. You'll need to see the new doctor several times to establish that he or she is your treating doctor.
How can you discern whether or not your doctor will support your disability claim when filling out an RFC form (that is, accurately reflect your limitations and pain)? A brief conversation with your doctor may settle the issue quickly. Or you can review your own medical records to find out the extent to which your medical provider will be helpful...or not.
The bottom line is simply this: Social Security disability and SSI cases take too long to pursue, and are too hard to fight, only to find at the last moment that a doctor will not be supportive of your claim for disability benefits.