Diagnosis
The two most common culprits for a Keurig K-Supreme brewing only a partial cup are a clogged exit needle or internal mineral scale buildup. The exit needle is responsible for piercing the K-Cup lid and allowing brewed coffee to flow into your cup. If it's blocked by coffee grounds or pod debris, the flow will be severely restricted or stop entirely, causing the brewer to finish its cycle prematurely. Alternatively, scale accumulation inside the internal tubing and heating element restricts water flow and can trick the machine's sensors into thinking a full brew cycle has completed.
How to Fix It
Start by cleaning the exit needle. First, ensure the machine is unplugged and cool. Remove the K-Cup pod holder assembly from the brewer. Detach the funnel from the top of the pod holder. Inspect the small, pointed exit needle located on the interior bottom of the holder. Using a straightened paper clip, carefully insert it into the tip of the needle several times to dislodge any compacted grounds. Rinse the entire pod holder assembly thoroughly under warm water. Reassemble and test with a fresh K-Cup and water reservoir filled to the Max line.
If That Didn't Work
If cleaning the needle doesn't resolve the issue, your machine likely needs descaling. Follow the official Keurig descaling procedure: fill the reservoir with descaling solution and water, initiate a descale cycle through the machine's menu (or by holding the appropriate buttons), and run multiple brew cycles without a K-Cup until the reservoir is empty. Then, perform several rinse cycles with fresh water to flush out any remaining solution. Also, check that the water reservoir is seated correctly on its base and that the intake valve at the bottom of the reservoir is not obstructed.
Heads Up
Use only Keurig-approved descaling solution or white vinegar; harsh chemicals can damage internal components. If you have performed two full descaling cycles and thoroughly cleaned the exit needle, but the problem persists, there may be a deeper internal fault, such as a failing water pump or a blocked internal line, requiring contact with Keurig Customer Support.