Fibbing is far from what endocrinologist Munira Siddiqui wants to hear in her office.

"It can be very detrimental to your health,” says Dr. Siddiqui, endocrinologist at Morton Plant Mease Hospital.

Dr. Siddiqui treats diabetics, so she has to know exactly how much sugar they eat in order to prescribe the right amount of insulin.

"By adjusting your insulin based on blood sugars that are false, I could have done harm to this patient," Dr. Siddiqui said.

She’s even had to fire a fibbing patient.

"They were actually making up their blood sugar numbers and the reason why they did it is that they knew I wouldn't give them samples if they would not have blood sugars when they came in to see me,” Dr. Siddiqui said.

Valeria Moore, PsyD, psychologist at Baycare Hospitals, also deals with dishonesty, a lot.

"Sometimes there’s outright, blatant lies.” explains Dr. Moore.

The red flags go up when the eye contact goes away.

Huffing, grunting, fidgeting, and re-asking a question are also signs of fiction.

"Well, what do you mean by that? Do you mean how much alcohol did I have yesterday or did you mean ever?" Dr. Moore said.

She says smoking, alcohol, and illicit drugs are what most of her patients lie about.

“We're running the risk of them going through withdrawal in the hospital, experiencing DTs, where they are at risk for seizure activity, perceptual disturbance and if we don’t know that, we can’t treat it and that puts the patient in very, very dangerous position as well as the other staff and other patients," Dr. Moore said.

Dr. Moore says they lie because they’re afraid of being judged.

Dr. Siddiquií's patients may lie because they fear they could lose insurance coverage.

A Cleveland Clinic survey showed that 28 percent of patients admitted to lying. But in a Wall Street Journal report, doctors say the real number is 77 percent.

"I do need people to be truthful. I need people to be honest. I need them to be compliant, in order to help them," Dr. Siddiqui said.

"There are always things that we want to hold and keep to ourselves," Dr. Moore said.

Apparently the lying goes both ways.

A study published in the Journal of Health Affairs last year found that over one-tenth of more than 1,800 physicians surveyed had told patients something untrue in the previous year.

More than half said they described a prognosis in a more positive manner than warranted and about 20 percent admitted to not fully disclosing a mistake to a patient due to fears of litigation.