Adjustments in Insulin Therapy
It is difficult to make general recommendations regarding insulin adjustments in dogs and cats. One of the most important
determinants in insulin adjustment is clinical signs. It may take dogs and cats several days to adapt to the introduction
of insulin. For this reason hyperglycemia should not be concerning in the newly diagnosed healthy diabetic and increases in
maintenance insulin are not typically recommended earlier than one week after instituting therapy. Patients may be monitored
after starting insulin therapy for hypoglycemia and appropriate reductions in insulin dose made. As stated previously, hypoglycemia
is fairy common with initiation of glargine insulin in cats but clinical signs of hypoglycemia are rare. In general if hypoglycemia
develops in dogs and cats, the dose of insulin is reduced by 25 - 50%. In some cases (e.g. Somogyi with excessive insulin
doses) it may be advisable to revert to a recommended initial dose. Remember in cats diabetic remission is possible so in
those on small amounts of insulin (</= 0.5 unit per dose) that develop hypoglycemia, discontinuation of insulin may be indicated.
Diabetic remission is much more common in newly diagnosed diabetic cats and does not typically occur in the dog.
Traditionally diabetics have been monitored with clinical signs (primarily water consumption and urine production), glucose
curves and serum fructosamine levels. Clinical signs continue to be important in evaluating a diabetic patient. A well-regulated
animal should no longer be polyuric, polydipsic, polyphagic and maintaining (or gaining) weight.
The following discussion pertains to stable diabetics. A glucose is sometimes performed on cats initially placed on glargine
or detemir for up to 72 hours because of the high incidence of hypoglycemia but in most instances curves are not performed
earlier than 7 days after initiation of therapy. Curves are then performed every 7 to 14 days until a stable insulin dose
has been determined. In-hospital glucose curves had long been the mainstay of diabetic monitoring. It is often difficult to
get animals to mimic their lifestyle in the hospital including activity level and caloric consumption that may affect blood
glucose levels. In-hospital glucose curves are particularly problematic in cats due to stress hyperglycemia. The impact of
these factors can be minimized by having owners perform glucose curves at home. Glucose curves should consist of a pre-insulin/meal
glucose and the nadir. The number of samples required varies patient to patient and with insulin types. With intermediate-acting,
more potent insulins (NPH, lente), more glucose measurements may be necessary to determine the nadir because it can occur
at various times and be quite dramatic over a shorter period of time. This is the basis for the traditional recommendation
of glucose checks every 2 hours. For the less potent, 'peakless' insulins (glargine, detemir) a pre-administration glucose
followed by measurements every 3 to 4 hours until the next insulin dose may be adequate. Glucose curves for diabetic ketoacidosis
and sick diabetics require more intense monitoring than stable diabetics.
It is also important to remember that human glucometers are designed to measure venous blood glucose in people and are not
necessarily accurate in dogs and cats. These glucometers also often read 30 mg/dl lower to protect diabetics from hypoglycemia.
When utilizing glucometers calibrated for dogs and cats, there is a difference in recommendations made. The following are
recommendations utilizing glucometers calibrated for dogs and cats. In general when using glucometer calibrated for dogs and
cats, a pre-insulin glucose < 250 mg/dl and a nadir between 100 and 150 mg/dl are ideal. In the cat, a pre-insulin glucose
< 250 mg/dl in the cat with a nadir between 100 and 150 mg/dl is desirable. Increases in the dog depend on the current dose
and degree of glucose elevation but do not usually exceed 20 to 25% or 0.5 to 1 unit in the cat. Reductions are dependent
on the nadir and presence of clinical signs but are typically approximate 50%. When weaning cats off insulin it is recommended
they be gradually decreased to 0.5 units per dose and then insulin discontinued. Regarding duration, if giving twice daily
insulin and the nadir occurs within 3 hours or the duration is < 8 hours a longer-acting formulation should be considered.
If the duration is greater than 12 hours (nadir > 8 hours) the options are once daily administration or twice daily administration
at a lower dose.
Fructosamine is a measure of glycated proteins in the serum and is a reflection of glucose levels over 2 to 3 weeks time.1 Fructosamine can also help eliminate concerns of stress hyperglycemia in cats but there are many factors that affect fructosamine
so using them as a sole guide for insulin therapy is not recommended. Signs of hyperglycemia in the face of an elevated fructosamine
should prompt a glucose curve to assess glycemic control.