Three patients with insulin-dependent diabetes mellitus are described in whom 
generalized oedema and weight gain followed the administration of excessive 
monocomponent insulins, in two cases associated with symptomatic hypoglycaemia. 
Serial measurements of plasma volume and transcapillary escape rate of albumin 
(TERA) using 125I-labelled albumin, serum colloid osmotic pressure (COP) using a 
membrane colloid osmometer, packed cell volume (PCV), and serum proteins, showed 
that oedema was associated with an increased plasma volume and TERA, while serum 
albumin and total protein concentration and serum COP were reduced. A reduction 
in daily insulin dose abolished hypoglycaemia and resulted in weight loss, 
natriuresis, diuresis, a reduction in plasma volume and TERA, and an increase in 
serum albumin, total protein, and COP. Strict metabolic control in previously 
poorly controlled patients may cause insulin-induced increments in plasma volume 
and albumin escape rate.