We describe a patient who presented on two occasions with severe hypobicarbonatemia and an associated high anion gap on enzymatic analysis. She also had profound hyperlipidemia. Her low bicarbonate was shown to be factitious by analysis of her blood using a direct ionselective electrode method. Reanalysis of blood samples after treatment with a lipid clearing agent resulted in marked improvement in the bicarbonate level. We suggest that the light scattering effect of the hyperlipidemia interfered with the photometric analysis causing this factitious phenomenon.