There is a relatively narrow gap between therapeutic and toxic
serum levels of
digoxin. Normal therapeutic levels are about one-third of those that are fatal, and serious toxic arrhythmias begin at about two-thirds of the fatal levels. The normal range for
digoxin levels is 0.8 to 2 nanograms/mL (or 1.02 to 2.56 nanomol/L). To convert nanograms/ mL to nanomol/L multiply by 1.28, or to convert nanomol/L to nanograms/mL
multiply by 0.781. Note that micrograms/L is the same as nanograms/mL. If a patient is over-digitalised, signs and
symptoms of
toxicity will occur, which may include loss of appetite, nausea and vomiting, and bradycardia. These effects are often used as
clinical indicators of
toxicity, and a pulse rate of less than 60 bpm is usually considered to be an indication of over-treatment. Other
symptoms include visual disturbances, headache, drowsiness and occasionally diarrhoea. Death may result from cardiac arrhythmias. Patients treated for cardiac arrhythmias can therefore demonstrate arrhythmias when they are both under- as well as over-digitalised.