Calcitriol Dosing and Fasting

The following was derived from four 2008 emails from Dr. Nagode with Dr. Nagode quoted extensively below.  Dr. Nagode stresses that all decisions on dosing and fasting should be taken in consultation with the treating veterinarian.  The information below is a guideline to help in the dosing and fasting decisions.  In general, Dr. Nagode believes " when calcium levels are at or near top of the normal range, fasting is indicated no matter whether dosing daily or intermittently (each 3.5 days) with the first option pursued when calcium runs high being use of intermittent [every 3.5 days] dosing which is much more powerful versus hypercalcemia than fasting the daily dosed patient."  Dr. Nagode currently recommends two dosing schemes daily and every 3.5 days. He no longer endorses "every other day" (EOD) dosing.

(David Jacobson, March 2008)



Fasting?? (See foot notes)

Serum Calcium Levels 

Daily Dose

Every 3.5 Day Dose

Near the Top of the Normal Range or Higher

Recommended (1)(3)

Recommended (3)

Mid-Range Normal to Top Half of Normal Range

Not Necessary (1)

Advisable (2)

Lower Normal Range

Not Necessary (1)

Desirable (4)



  1. Daily Dosing. Fasting is unnecessary UNLESS the cat's calcium is high normal or higher. Dr. Nagode's preference is always for animals with calcium issues to receive every 3.5 day dosing but if that's not possible and daily dosing is necessary, he recommends that cats with high normal or elevated calcium be fasted. He suggests a pre-fast running 2-4 hours and a post-fast from 30 minutes-1 hour the higher the calcium values, the longer the pre and post fasts. (see #3 below for more details on suggested fasts). 
  1. For animals on every 3.5 day dosing with calcium below top-end of normal.  Fasting is not required if the animal's serum calcium is in the lower-half of the normal range. For cats with serum calcium in the upper half of the normal range but lower than the top-end of said range, Dr. Nagode suggests a minimal fast --- 1 hour before calcitriol administration and 15-30 minutes after. "Although doses each 3.5 days are higher than daily doses, I would rather use the terminology that "fasting is advisable" rather than mandatory. This would be particularly true for the somewhat unusual case in which the calcium levels were running on the low side and owner wished (presumably for economic reasons) to dose each 3.5 days--then fasting would be of little value. As a precaution, for those with calcium [values] running from mid-normal range to upper limit of normal, however, I would say that it's advisable--but would not wish to go to mandatory" with final judgments made in consultation with the local veterinarian who is on the scene and can make judgments based on all the information at hand." 
  1. For cats on every 3.5 day dosing with calcium values at the top end of the normal range or higher, Dr. Nagode recommends fasting. "My definition of a fast is conditional upon how marked the calcium problem is. For truly worrisome elevations like over 13 mg/dl total calcium both going to intermittent dosing and a 3-4 hour before, 1 hour after would be indicated. Milder elevations could go with say 2 hour, 30 minute approach with extent of fast modifiable depending upon what the results of subsequent blood calcium checks were. All of these strategies are impacted by outcomes (resulting blood calcium levels) and modifiable also in accord with how the outcomes fall out. Setting hard and fast protocols are therefore --although seemingly desirable--better avoided with a "feeling the way" to best outcome almost always the better approach." 
  1. Last, even for cats being dosed every 3.5 days and in the lower half of the normal range, Dr. Nagode suggests in his protocol that " when doses  > 5 ng/kg are needed [Editor:  every 3.5 days doses are all  > 5 ng/kg] best given at bedtime on an empty stomach to prevent hypercalcemia." But Dr. Nagode expands on this in the following, noting that it's desirable rather than necessary and may be precluded by the circumstances of an instant case. "  it [every 3.5 day dosing] has come into use probably more than for any other reasons for financial ones in that it is cheaper and almost certainly (evidence is not as complete as many would wish) just as effective as daily dosing and thus in instances in which hypercalcemia is not feared or existing empty stomach dosing is not as critical. Is it recommended? I would say, yes it is likely wise. Is it MANDATORY? -- I would say no --in many instances such as in particular those described by a [Yahoo Calcitriol] group member ... who had great problems due to many circumstances in keeping her cat  adequately fed [due to] many such factors, therefore, I think it is better to use terms like "suggested." etc., rather than required," although the  latter may be more satisfying for the purposes of creating guidelines, they for one thing cut the local veterinarian's judgment (which can be very valuable considering those factors which impact the "whole picture") out of the picture leading owners to views that they "must" do things in a rigid defined way when this may or may not be the case depending upon circumstances.