Dosage Practice

mcg/kg/min Calculation: Weight-Based IV Drips in mL/hr

Multiply the dose by the weight to get mcg per minute, multiply by 60 to get mcg per hour, then divide by the bag's concentration in mcg per mL to get mL per hour. The concentration is the drug amount in the bag divided by the bag's volume.

The Formula

mL/hr = (mcg/kg/min × kg × 60) ÷ (mcg per mL in the bag)

Concentration: mg in bag × 1,000 ÷ mL in bag = mcg/mL.

How to work it out

  1. 1 Work out the bag's concentration in mcg/mL. 400 mg in 250 mL is 400,000 mcg ÷ 250 mL = 1,600 mcg/mL.
  2. 2 Multiply the ordered mcg/kg/min by the weight in kg: that is mcg per minute.
  3. 3 Multiply by 60: mcg per hour.
  4. 4 Divide by the concentration: mL per hour. Round to the nearest tenth, since critical care pumps accept tenths.

Worked Examples

Example 1

Dopamine 400 mg in 250 mL. Ordered: 5 mcg/kg/min for an 80 kg patient. Pump rate in mL/hr?

  1. Concentration: 400,000 mcg ÷ 250 mL = 1,600 mcg/mL.
  2. 5 × 80 = 400 mcg/min.
  3. 400 × 60 = 24,000 mcg/hr.
  4. 24,000 ÷ 1,600 = 15 mL/hr.

Answer: 15 mL/hr

Example 2

A bag is 800 mcg/mL. Ordered: 3 mcg/kg/min for a 70 kg patient. Pump rate?

  1. 3 × 70 = 210 mcg/min.
  2. 210 × 60 = 12,600 mcg/hr.
  3. 12,600 ÷ 800 = 15.75, rounded to 15.8 mL/hr.

Answer: 15.8 mL/hr

Try five free problems

One exact answer, rounded as asked, no partial credit. No sign-up needed.

Problem 1 of 3No sign-up needed

The bag contains 1,600 mcg/mL. Ordered: 5 mcg/kg/min for a 60 kg patient. Pump rate in mL/hr?

Round to the nearest tenth

mL/hr

Common Mistakes

  • Forgetting the mg to mcg step in the concentration

    400 mg in 250 mL is 1.6 mg/mL, which is 1,600 mcg/mL. Using 1.6 as if it were mcg/mL makes the rate a thousand times too high.

  • Leaving the answer per minute

    Pumps run per hour. After multiplying dose by weight, multiply by 60 before dividing by the concentration.

  • Using pounds

    The dose is per kilogram. Convert 176 lb to 80 kg before you start.

Questions Students Ask

Why round to tenths here when other pumps take whole numbers?

Critical care pumps accept tenths of a milliliter per hour because these drugs are titrated in small steps. The question will tell you if a whole number is expected.

How do I go the other way, from mL/hr to mcg/kg/min?

Multiply the rate by the concentration to get mcg per hour, divide by 60 for mcg per minute, then divide by the weight.

Keep practicing in lesson 12: Weight-Based Drips (mcg/kg/min)

Fresh numbers every time. Ten correct answers finish the lesson. The practice round and the first five problems of lesson 1 are free.

Open lesson 12