Numbness in the feet, known as paresthesia, is a common experience ranging from a momentary annoyance to a sign of a serious underlying condition. This sensation is described as a temporary loss of feeling, prickling, burning, or the familiar tingling of “pins and needles.” Paresthesia occurs when the signaling pathway between the nerves in the foot and the central nervous system is disrupted.
Temporary Nerve Signals: Why Your Foot “Falls Asleep”
The most frequent cause of foot numbness is transient positional compression, commonly known as your foot “falling asleep.” This happens when sustained external pressure, such as sitting cross-legged or kneeling, compresses a peripheral nerve. The pressure temporarily blocks the nerve’s ability to transmit signals to the brain, leading to a loss of feeling.
An intense tingling and prickling follow when the pressure is removed. This occurs as the nerve fibers begin to fire erratically while sensation and blood flow return to the area. This temporary disruption is harmless, resolving quickly once the position is changed and the nerve regains its normal function. Moving or shaking the limb restores proper signaling and sensation.
Systemic Causes: Numbness Related to Underlying Disease
Chronic numbness that persists or worsens often indicates peripheral neuropathy. The leading cause of this type is uncontrolled blood sugar associated with diabetes, known as diabetic neuropathy. High glucose levels over time damage the small blood vessels that supply oxygen and nutrients to the nerve fibers.
This metabolic damage causes the nerve fibers to degenerate, typically affecting the longest nerves first. The resulting numbness usually presents symmetrically in both feet, often described as a “stocking-glove” pattern. Other systemic conditions can also cause this type of internal nerve damage, including kidney disorders, chronic alcoholism, and severe Vitamin B12 deficiency. These lead to persistent symptoms that are not relieved by simply changing position.
Physical Impingement and Nerve Traps
Numbness can also stem from physical structures compressing the nerve pathway, often originating outside the foot itself. Sciatica is a common example, where the root of the large sciatic nerve is compressed in the lower back, usually by a herniated disc or spinal stenosis. This compression causes radiating pain, tingling, and numbness that travels down the leg and into the foot.
Local nerve entrapments can also cause specific patterns of foot numbness. Tarsal Tunnel Syndrome involves the compression of the posterior tibial nerve as it passes through a narrow channel in the ankle. This nerve trap can be caused by inflammation, fluid retention, or structural issues like flat feet that put pressure on the nerve. Persistent external factors, such as wearing poorly fitted or excessively tight footwear, can also create chronic compression on localized nerves, leading to numbness.
When Foot Numbness Requires a Doctor Visit
While temporary numbness is normal, certain signs should prompt a professional medical evaluation. Seek care if the numbness in your foot is persistent, progressively worsens, or does not resolve after changing position. Numbness that spreads quickly or is accompanied by sharp, burning pain also warrants a doctor’s visit.
Immediate medical attention is necessary if the numbness occurs suddenly and is paired with other neurological symptoms. These “red flags” include significant muscle weakness, difficulty walking, loss of balance, or loss of bladder or bowel control. Any foot numbness that develops following a recent injury or trauma should be evaluated quickly.