Reference values for 24-hour urinary potassium excretion during pregnancy. Physiologic changes in renal handling and maternal potassium balance produce trimester-specific variations in normal urinary K⁺ loss.
| Units | Non-pregnant Adult | 1st Trimester | 2nd Trimester | 3rd Trimester |
|---|---|---|---|---|
| mmol / 24 hr | 25–100 | 17–33 | 10–38 | 11–35 |
Causes of High 24-Hour Potassium Excretion (Renal K⁺ Wasting)
- High potassium intake (diet or supplements)
- Diuretics (loop, thiazide)
- Renal tubular acidosis (Type 1 or 2)
- Primary or secondary hyperaldosteronism
- Cushing syndrome or exogenous glucocorticoids
- Hypomagnesemia (impairs potassium reabsorption)
- Vomiting → metabolic alkalosis with renal potassium loss
- Osmotic diuresis (e.g., uncontrolled diabetes)
- Medications:
- Beta-agonists
- Aminoglycosides
- Amphotericin B
- Genetic tubular disorders:
- Bartter syndrome
- Gitelman syndrome
Causes of Low 24-Hour Potassium Excretion
- Low dietary potassium intake
- Potassium-sparing diuretics (spironolactone, eplerenone, amiloride)
- ACE inhibitors / ARBs
- NSAID use
- Adrenal insufficiency (low aldosterone)
- Chronic kidney disease (reduced distal secretion)
- Severe volume depletion
- Medications reducing distal K⁺ secretion:
- Heparin (aldosterone suppression)
- Trimethoprim (blocks ENaC)
- Incomplete 24-hour urine collection
References
- Abbassi-Ghanavati M, Greer LG, Cunningham FG. Pregnancy and laboratory studies: a reference table for clinicians. Obstet Gynecol. 2009;114:1326–1331. PMID: 19935037