Workup for Nocturnal Foot Cramps
The workup for nocturnal foot cramps should focus on identifying secondary causes through targeted history, medication review, physical examination, and selective laboratory testing—most cases are idiopathic and require minimal investigation unless red flags are present. 1, 2
Clinical History
Differentiate from mimicking conditions by asking specific questions:
- Restless Legs Syndrome (RLS): Ask "What does it feel like?", "Does it vary over the day and is it worse later in the day/evening?", "Is it relieved by movement?", and "Does it come back again a few minutes after you sit or lie back down?" 1
- Periodic Limb Movement Disorder: Ask "Does your bed partner complain that you have twitchy legs or make kicking movements in your sleep?" 1
- Timing and characteristics: Document frequency, duration, location, and severity of cramps 2
Screen for underlying systemic conditions using these questions:
- Ankle swelling (cardiac, renal disease) 3
- Shortness of breath on exertion (cardiac, renal disease) 3
- Excessive thirst (diabetes, endocrine disorders) 3
- Problems controlling legs, slowness of movement, tremor (neurological disease) 3
- Lightheadedness on standing (cardiovascular, neurological issues) 3
Medication Review
Review all medications as several drug classes are strongly associated with nocturnal leg cramps:
- Diuretics 1, 4
- Calcium channel blockers 1
- Lithium 1
- NSAIDs 1
- Intravenous iron sucrose, conjugated estrogens, raloxifene, naproxen, and teriparatide 2
- Long-acting beta-agonists 4
Physical Examination
Perform targeted examination focusing on:
- Peripheral edema 3
- Lower limb weakness, abnormalities of gait or speech, tremor 3, 1
- Blood pressure measurement 3
- Signs of vascular disease 1
Laboratory Investigations
Order baseline laboratory tests only if secondary causes are suspected based on history or examination:
- Electrolytes and renal function 1
- Thyroid function 1
- Calcium 1
- HbA1c 1
- Serum ferritin if RLS is suspected (values <50 ng/mL indicate iron deficiency) 1
Key Clinical Pearls
Most nocturnal leg cramps are idiopathic and caused by muscle fatigue and nerve dysfunction rather than electrolyte abnormalities—extensive laboratory testing is usually unnecessary unless the history or physical examination suggests a specific underlying condition 2, 5.
Associated medical conditions to consider include vascular disease, lumbar canal stenosis, cirrhosis, hemodialysis, and pregnancy 2.
Avoid quinine for treatment or prevention—the FDA has issued a boxed warning that quinine use for nocturnal leg cramps may result in serious and life-threatening hematologic reactions including thrombocytopenia and hemolytic uremic syndrome/thrombotic thrombocytopenic purpura, and the risks outweigh any potential benefit 6.