Gone Fishin’

Gone Fishin’

“Doc, I’m not gettin’ my metformin,” my disgruntled patient announced.

“What do you mean? Metformin is cheap and very accessible.”

“No, I mean I’m not absorbing it. I see the whole pill come out in my poop.”

Ah. The infamous toilet diagnosis.

“Well, that doesn’t necessarily mean you’re not getting the medication,” I explained. “The extended-release form of metformin is designed to release the drug slowly as it travels through your GI tract. Sometimes the outer shell or tablet matrix passes through and shows up in the stool.”

He looked at me as if I had just suggested his colon had taken up arts and crafts.

“That makes no sense. I see the whole pill.”

“I understand why it looks that way,” I said. “But what you’re seeing is usually the empty delivery shell. Think of it like a tea bag. The tea seeps out into the water, but the bag is still there afterward. In this case, the medicine has already seeped out and been absorbed. What you’re seeing in the toilet is the used-up wrapper, not the full dose.”

He remained unconvinced.

I went deeper, because apparently we were now holding grand rounds over a bowel movement.

“Metformin XR is made so the active drug slowly leaves the tablet as it moves through the gut. Some extended-release tablets use an insoluble or partly insoluble framework, almost like a sponge. Fluid enters the tablet, the medication dissolves, and the dissolved drug gradually diffuses out. The leftover framework can stay intact enough to be visible in the stool.”

He narrowed his eyes.

“I can bring it in and show you.”

Of course he could.

Patients will forget their glucose meter, their medication list, their insurance card, and the name of the pharmacy they have used for twenty-three years, but suggest that something medically interesting has appeared in the toilet and suddenly they become forensic evidence technicians.

“If you’d like to pilfer through your poop and bring in the metformin shells, that’s up to you,” I said. “But I do charge an extra fee for fecal focus.”

That caught his attention.

“How much?”

“Enough to make trusting me the more economical option.”

He leaned back and considered this.

“Well, Doc, I guess I’ll just take your word for it.”

“Wise decision,” I said. “Just go with the flow.”

Neither of us could hold a straight face.

In medicine, not every mystery requires a specimen cup. Sometimes the patient is absorbing the medication just fine. Sometimes the pill is only a ghost of its former self. And sometimes the best clinical advice is simple:

Leave fishing expeditions to the anglers.