When a doctor pops up in your Facebook feed or Twitter account advising you to take a particular medication, how can you be sure it’s not because he or she has accepted money from the drug’s makers?

The answer: You can’t.

That’s the take-home message of a new investigative that found American physicians who routinely offer medical advice on social media often fail to mention that they have accepted tens and sometimes hundreds of thousands of dollars from the companies that make the prescription drugs they tout.

A Boston Globe examination of hundreds of social media accounts shows that healthcare professionals rarely note their conflicts of interest, some of them significant, when promoting drugs or medical devices on Facebook, Instagram, and Twitter.

Among the findings:

•    Women’s health specialists who serve as consultants for the company that developed Addyi, the female libido drug, use Twitter to promote the drug and related treatments.
•    A child psychiatrist featured on YouTube steers viewers to the website for Saphris, an antipsychotic drug made by Allergan, which pays her to promote it.
•    An internist’s Facebook posts about the positive effects of a cholesterol drug fail to reveal the medication’s manufacturer paid him nearly $60,000.

There is no evidence these doctors are deceiving or misleading patients, and they are not legally obligated to disclose payments from drug companies. But the report’s findings are a wake-up call about a driving force behind the growing use of social media by medical professionals to promote medications.