Officials say insulin pens that were only supposed to be used once were used for multiple people.
The department of Veterans Affairs has informed congress that this was happening at the buffalo VA Medical Center for the past two years.
According to the Centers for Disease Control, there should be no sharing of the pens, even when the needles are discarded.
If this doesn't happen, patients who are injected with reused pens could be infected.
The VA is offering free blood tests to patients who may be at risk.