An extensive review of the literature found that heparin
(both unfractionated and low- molecular-weight heparins) and heparinoids inhibit the secretion of aldosterone, which can cause hyperkalaemia. This may be additive with the hyperkalaemic effects of ACE inhibitors
The CSM in the UK suggests that potassium should be measured in all patients with risk factors (e.g. renal
mellitus, pre-existing acidosis and those taking potassium-sparing drugs) before starting heparin, and monitored regularly thereafter (every 4 days has been suggested) particularly in patients receiving heparin
for more than 7 days.