Short answer: Yes. Insulin labels state that all insulins move potassium from the blood into cells, which can lead to low blood potassium (hypokalemia). The labels say untreated hypokalemia can be life-threatening, and that potassium is monitored in people at higher risk, such as those on potassium-lowering medicines, those on medicines sensitive to potassium levels, and anyone getting insulin into a vein.
The Humalog and Lantus labels say all insulins cause a shift in potassium from the fluid outside cells to the inside of cells, possibly leading to hypokalemia; the NovoLog label says they can. All three warn that untreated hypokalemia may cause respiratory paralysis, dangerous heart rhythms and death.
The labels advise monitoring potassium in people at risk, giving two examples: people using potassium-lowering medicines, and people taking medicines whose effects depend on potassium levels. When insulin is given into a vein, the labels say it is done only under medical supervision with close monitoring of both blood sugar and potassium. The Humalog label also lists hypokalemia, along with low blood sugar, as a result of taking too much insulin.
MedlinePlus lists common causes of low potassium: medicines such as diuretics (water pills), diarrhea or vomiting, laxative overuse, heavy sweating, low magnesium, chronic kidney disease, and some hormone conditions. These can add to the effect of insulin.
Steroids are another example. The prednisone label lists potassium loss and hypokalemia among its side effects, says people taking it with potassium-depleting medicines such as diuretics should be watched for hypokalemia, and warns that people on digitalis medicines such as digoxin may be at higher risk of abnormal heart rhythms from low potassium.
Some medicines push potassium the other way. Spironolactone, for example, can raise it (see potassium and spironolactone). This is one reason a full medicine list matters when potassium results are read.
MedlinePlus says a small drop often causes no symptoms, or mild ones such as constipation, a feeling of skipped heartbeats, tiredness, muscle weakness or spasms, and tingling or numbness. A large drop can cause abnormal heart rhythms, especially in people with heart disease, which can make someone feel lightheaded or faint.
Potassium is checked with a blood test. MedlinePlus gives a normal range of 3.5 to 5.1 mEq/L, and says an ECG may also be done. Mild low potassium is often treated with potassium pills, and severe low potassium with potassium through a vein.
The label wording is about monitoring when it is indicated, not routine testing for everyone. Whether and how often potassium is checked depends on the other medicines, kidney function and health conditions, and is set by the prescriber. Dose Track can keep lab results next to insulin doses and other medicines, which helps when a result needs to be read in context.
Read more on Dose Track: Hypokalemia · Humalog side effects · Lantus side effects · Blood sugar