How many grams of glucose are needed to prepare 400 mL of a?

Glucose solutions are commonly used in medical settings as a source of calories and water for patients who are unable to eat or drink normally. Preparing the right concentration of glucose solution is important for delivering the correct dose of glucose to the patient. This article will provide a step-by-step explanation of how to calculate the grams of glucose needed to prepare 400 mL of a 5% glucose solution.

Quick Answer

To prepare 400 mL of a 5% glucose solution, 20 grams of glucose are needed.

Step-by-Step Calculation

Follow these steps to calculate the grams of glucose needed:

  1. Identify the desired concentration of the glucose solution as 5%
  2. Identify the desired final volume of glucose solution as 400 mL
  3. Convert the percentage concentration to a decimal: 5% = 0.05
  4. Use the formula: grams of solute = (concentration in decimal form) x (final volume in mL)
  5. Plug in the numbers:
    • Concentration = 0.05
    • Final volume = 400 mL
  6. Calculate:
    • Grams of glucose = (0.05) x (400 mL)
    • Grams of glucose = 20 grams

Therefore, to prepare 400 mL of a 5% glucose solution, 20 grams of glucose are required.

Explanation of Calculations

Let’s go through an explanation of each step in the calculation:

1. Identify the concentration and final volume

We are told that the desired concentration of the glucose solution should be 5%. This means 5 grams of glucose per 100 mL of solution.
We are also told the desired final volume is 400 mL.

2. Convert percentage to decimal

To use the formula, we need to convert the percentage concentration to a decimal. 5% equals 0.05 when converted to a decimal.

3. Use the formula

The formula for calculating grams of solute is:

Grams of solute = (Concentration in decimal form) x (Final volume in mL)

4. Plug in the numbers

We can plug our given values into the formula:

  • Concentration = 0.05
  • Final volume = 400 mL

5. Calculate

Performing the calculation gives us:

Grams of glucose = (0.05) x (400 mL) = 20 grams

Therefore, 20 grams of glucose are required to prepare the 5% glucose solution with a final volume of 400 mL.

Why the Volume and Concentration Matter

It’s important to accurately calculate the required grams of glucose based on the desired concentration and final volume. Here is why the volume and concentration are important:

Delivering the correct dose

The concentration and volume determine the total dose of glucose delivered to the patient. A 5% glucose solution contains 5 grams of glucose per 100 mL. If the concentration is too low, the patient may not receive adequate glucose. If it’s too high, the patient may receive excess glucose.

Avoiding adverse effects

Excessively high or low glucose concentrations can have adverse effects on the patient. Side effects of excessive glucose include high blood sugar, dehydration, and hyperosmolar coma. Low concentrations may lead to hypoglycemia and electrolyte imbalances.

Achieving appropriate fluid balance

The volume of the solution determines the amount of fluid the patient receives. This affects their fluid and electrolyte balance. An appropriate volume should be prepared to avoid under or over hydrating the patient.

Tips for Preparing Glucose Solutions

Here are some useful tips for preparing glucose solutions accurately:

Use an accurate scale

Measure the glucose powder carefully using a calibrated scale to ensure the correct mass is obtained.

Mix thoroughly

After adding the glucose powder to water, mix thoroughly to ensure it fully dissolves and is evenly distributed within the solution.

Use volumetric glassware

Prepare the solution in volumetric flasks or graduated cylinders to accurately measure volumes.

Label clearly

Label the solution container clearly with the concentration, volume, and expiration date.

Check concentrations

Use glucose test strips to verify the final concentration, especially for very dilute or concentrated solutions.

Store properly

Store solutions according to manufacturer’s instructions to maintain stability.

Clinical Uses of Glucose Solutions

Here are some common clinical uses of intravenous glucose solutions:

Fluid replacement

Glucose solutions can help replace fluid volume losses from vomiting, diarrhea, wounds, burns, or surgery.

Calorie supplementation

Glucose solutions provide a source of calories when patients cannot meet needs through diet alone.

Low blood sugar

Glucose solutions can help increase blood sugar levels in hypoglycemic patients.

Electrolyte imbalance

Glucose solutions may be used to correct electrolyte imbalances like low potassium or low phosphorus.

Carbohydrate loading

High glucose doses help maximize glycogen stores before surgeries, burns, and other stresses.

Drug delivery

Glucose solutions can serve as a diluent and vehicle for intravenous medications.

Examples of Glucose Solution Preparation

Let’s look at a few examples of calculating grams of glucose for different volumes and concentrations:

Example 1

How many grams of glucose are needed to prepare 500 mL of a 10% solution?


  1. Convert 10% to decimal: 10% = 0.10
  2. Volume is 500 mL
  3. Use formula: Grams glucose = (0.10) x (500 mL) = 50 grams

Example 2

How many grams of glucose are needed to prepare 1 liter of a 15% solution?


  1. 15% = 0.15
  2. 1 liter = 1000 mL
  3. Grams glucose = (0.15) x (1000 mL) = 150 grams

Example 3

How many grams of glucose are required to make 250 mL of a 2.5% solution?


  1. 2.5% = 0.025
  2. Volume is 250 mL
  3. Grams glucose = (0.025) x (250 mL) = 6.25 grams

As shown in the examples above, the grams of glucose required depends on the desired percentage concentration and the final volume of solution.

Considerations for Specific Patient Populations

Special considerations may be necessary when calculating glucose solution doses for certain patient populations:

Pediatric patients

– Require lower volumes and infusion rates compared to adults.
– Doses are calculated based on weight or body surface area.

Renal impairment

– May require decreased concentration and volume to avoid fluid overload.
– Glucose may accumulate due to impaired excretion.


– Need careful glucose monitoring to avoid hyperglycemia.

– Insulin therapy should be coordinated with glucose administration.

Hepatic impairment

– Impaired glucose metabolism may require lower glucose doses.
– Monitor for signs of hepatic encephalopathy which can be exacerbated by glucose.


– Gestational diabetes requires tight glucose control.
– Fetal effects from maternal hyperglycemia may occur.

Safety Precautions for Glucose Solutions

Take the following safety precautions when working with glucose solutions:

  • Double check glucose calculations to prevent errors.
  • Use aseptic technique to avoid bacterial contamination of solutions.
  • Don’t use damaged or expired glucose containers.
  • Administer with an infusion pump to control flow rate.
  • Monitor patient’s glucose levels and watch for signs of excess or insufficient glucose.
  • Follow hospital protocols for safe handling and preparation of intravenous solutions.


Determining the correct amount of glucose when preparing intravenous solutions requires careful calculation based on the desired concentration and final volume. A simple formula allows calculation of the grams of glucose needed, but clinical judgement is also required to adapt doses for individual patients. Strict adherence to safety protocols helps avoid errors and prevent patient harm when working with glucose solutions.

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