What lab tests should I ask for if cramps keep happening at night?

The short version: no test in this evidence set has been shown to stop night cramps, and the one drug that does reduce them carries a small risk of a fatal blood reaction.

The honest starting point is that the records here are about treatment, not testing. Nothing in them tells you which lab test predicts or fixes cramps. What they do show is that the usual suspects are worth checking, because drugs and deficiencies both turn up as triggers.

Two prescription drug classes were linked to night cramps in a chart review of male veterans: nitrates and antidepressants, especially tricyclics [2]. A later study found that starting diuretics, statins, or long-acting beta-agonists was followed by more quinine prescriptions for cramps, strongest for beta-agonists and potassium-sparing diuretics [4]. That points to a practical test list: a basic metabolic panel for potassium and kidney function, and a magnesium level, since low magnesium is the deficiency most often blamed. The records do not prove those tests catch the cause, so treat them as reasonable screening, not a fix.

Quinine works but is not a safe routine fix: it cut about 3.6 cramps over four weeks versus placebo, and the effect shrank once unpublished trials were added, with more dropouts and side effects like ringing in the ears [2]. It can cause potentially fatal low platelets and hypersensitivity, and is contraindicated in pregnancy [1]. Calf stretching is the low-risk first step [2], though one trial found it did not help [3].

My call: ask for potassium, kidney function, and magnesium, and review your drug list first, because the drug link is the best-supported lead here. Confidence: moderate on the drug review, low on the labs.