INSULIN INITIATION

 

TAKE HOME MESSAGES:

 starting insulin is the “tip of the iceberg”.  What you/the patient do after insulin is started is MUCH MORE IMPORTANT.  If you will/can not titrate, don’t bother starting insulin!

tailor your choice of insulin regimen to the PATIENT

 ALWAYS ensure the patient knows how to detect and treat HYPOGLYCEMIA once insulin is started

 

When starting insulin ask yourself 3 questions:

    1. Does the patient need insulin?

    2. How much?

    3. What type(s) of insulin match my patient’s needs?

 

 

Step 1:  Does the patient need insulin?

Consider initiating insulin therapy if:

   A1C > target on maximal OAHAs (i.e. >7.0% on 3 OAHAs)

   severe hyperglycemia at diagnosis (i.e. fasting BG>14 mmol/L, random BG>17 mmol/L or A1C>10.0%)

   contraindications to OAHAs (e.g. ESRD, liver cirrhosis)

 

 Step 2: How much insulin?

   estimate the total daily dose (TDD), the total amount of insulin a patient may need in a day. This can be done by any of:

    - weight-based method:

     total daily dose of insulin = 0.5 units/kg

- however, if you have information about insulin that has already been given (e.g. via sliding scale), that could give you a more accurate assessment of the patient’s total daily insulin requirements

  for example, can count the total amount of insulin given to a patient via sliding scale, to use as a minimum TDD.  For example, if a patient has received 50 U/day via sliding scale alone, if the BG is still elevated despite this, make sure your TDD is at least 50 U/day (even if the weight-based formula gives you a lesser value).  

start low and TITRATE.  Remember, insulin is only as good as how you titrate.  You can use the above to give you good estimate of what is needed.  If concerned about risk of hypoglycemia, start low and titrate up. 

  generally divide the TDD into ~ 50% basal insulin and 50% bolus insulin (see section on insulin pharmacokinetics for a description of different types of insulin).  If using basal insulin together with OAHA’s, the OAHA’s try to [crudely] play the role of bolus insulin

 

Step 3:  What type(s) of insulin

    when determining the type of insulin regimen to start, consider all the following: results of capillary glucose monitoring, patient’s ability to check glucose, patient’s lifestyle and daily routine, risk for hypoglycemia, and patient finances

   there are three commonly-used insulin regimen

        - basal insulin only (or together with OAHA’s)

        - split-dose premixed regimen (for example, 30/70 given twice a day)

        - basal-bolus (e.g. multiple daily injections)

 

Basal insulin only:

  typically given as an intermediate (e.g. N, NPH) or a long-acting insulin (e.g. detemir or glargine) once daily

   advantages of this regimen:

       - simpler and convenient: one insulin, one injection

       - controls fasting glucose

       - useful if patient not able to monitor frequently (e.g. can titrate using just the morning BG)

       - less hypoglycemia and less weight gain (when used with OAHA’s) but as effective as 30/70 BID in terms of A1C lowering

  disadvantages of this regimen:

        - with time, may not be as effective to control glucose during the day (after meals)

 

Example:

50 year old man.  Weight 80 kg.  A1C 8.5% on maximal doses of metformin and glyburide.  Fasting glucose is consistently high (~12-15 mmol/L). What will you start him on?

 

Answer:

Using our steps as a guide:

 1.  Does he need insulin? 

      Yes - his A1C is high enough that adding another OAHA is unlikely to lower A1C to target.

 

 2.  How much to prescribe? 

     Using a weight-based formula, TDD = 0.5 u/kg = 40 U/day.

     50% would be basal = 20 U.  50% could be bolus.

 

 3.  What types of insulin match the patient’s need? 

He has high fasting glucose, so using basal insulin at night (and continuing his OAHA’s) is effective.  Could start 20 U qhs, but you would not be wrong to start lower (e.g. 10 U/day) for an insulin naïve patient BUT MAKE SURE TO TITRATE THE DOSE based on his fasting glucose.  For example, increase the basal insulin 2-4 units q2-3 days until the target BG is reached.

 

Split-dose, premixed regimens (e.g. insulin 30/70 twice daily):

   each dose gives a fixed percentage of a basal- and a bolus-type insulin

  Humulin or Novolin 30/70 contains 30% regular-acting insulin and 70% intermediate-acting insulin in each dose

   other options:

        -  Humalog Mix 25 (25% Lispro and 75% lispro protamine),

           Novomix 30 (30% Novolin Aspart and 70% aspart protamine)

        - lispro and aspart provide better postprandial coverage than Humulin R or Novolin Toronto, with less risk for hypoglycemia

 for starting doses, typically start ½ - of the TDD with breakfast and the rest with supper

advantages of this regimen:

        - provides both basal and bolus (e.g. mealtime) insulin

        - one insulin

        - due to the scheduling, CCAC can help reinforce its use after discharge

  disadvantages of this regimen:

        - increased risk for hypoglycemia, particularly in the elderly or those with other comorbidities

        - no flexibility in dosing or timing.  Could be an issue for the patient who does not have a set daily eating schedule

 

Example of dosing for this regimen:

You are looking after an 83 y.o male admitted with unstable angina with no documented DM.  He is found to have an A1C  of 11.3%.  He is unwilling to go on 4 insulin injections/day, but agrees to 2 injections/day.  He weighs 78 kg.  His BG is 10-12 mmol/L fasting, and increases to 15-18 mmol/L by supper. What will you start him on?

 

 Answer:

1.  Does he need insulin? 

    Yes, his A1C is markedly elevated.

2.  How much? 

    Total daily dose = (0.5 units/kg)(78 kg) = 39 U

3.  What types of insulin match my patient’s needs? 

 

Using just basal insulin at night may help his fasting BG, but may not be enough to help with the higher BG in the evening.  He will likely need more than just basal insulin.  Given he is unwilling to do multiple injections, a BID premixed regimen is reasonable.

Morning dose = 2/3 of TDD (39 units) = 26 units

Evening dose = 1/3 of TDD (39 units) = 13 units

Thus, could start 30/70 at 26 U qAM, 13 U qPM.  However, if starting insulin for the first time, can start at lower doses (e.g. 15 U qAM, 10 U qPM) PROVIDED YOU TITRATE the doses subsequently.

                   

Multiple daily injections:

  consists of a basal insulin given once or twice/day, PLUS bolus insulin with each meal

advantages of this regimen:         

        - allows more flexibility (helpful for patients who have unpredictable meal times/content and schedules)

        - more physiologic than the other two regimens

  disadvantages of this regimen:

        - works best if patient monitors before meals

        - more injections; less suitable for those who are less independent in function

 

Example:

Your patient is a 42 y.o executive admitted with a diabetic foot infection.  He weighs 84 kg.  He is on metformin 1000 mg bid, gliclazide MR 120 mg daily and sitagliptin 100 mg once daily, and is found to have an A1C of 9.2%.  He has both high fasting BG (10-12 mmol/L) and high BG at lunch (15-18 mmol/L) and supper (12-20 mmol/L).  What are you going to start him on?

 

 Answer:

1.  Does the patient need insulin? 

    Yes, his A1C is 9.2% despite three OAHA’s.

2.  How much? 

     Total daily dose of insulin = (0.5 units/kg)(84 kg) = 42 U as an estimate

3.  What types of insulin matches my patient’s needs? 

    If a patient has the skills and cognitive ability to use multiple daily injections (MDI), discuss the option with them.  In this case, you could use:

        Basal insulin = 0.5 x 42 U

                             = 21 U

 

        Bolus insulin = 0.5 x 42 U

                             = 21 U, or 7 U ac meals

 

Thus, this pt can be started on basal insulin 21 units sc qhs and bolus insulin 7 units sc with meals.  Again, if concerned about a patient’s risk should he/she become hypoglycemic (or lack of ability to detect hypoglycemia) start LOWER doses but TITRATE accordingly.

 

Housekeeping:

be sure the patient is informed about the risk for hypoglycemia, and explained the signs and symptoms of hypoglycemia and its TREATMENT prior to discharge

it can take 48-72 hours for a patient to learn how to use insulin properly and safely.  Make an early decision whether insulin will be required after discharge and arrange early referral to a Nurse Educator

  ensure pt has adequate medical follow-up after discharge to ensure BG is improving post-discharge and to watch for hypoglycemia

  don’t forget to write insulin prescription(s) when pt is discharged

 

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