Reading Time:

7 minutes

Insulin Pumps and CGMs Basics

Insulin pumps and Continuous Glucose Monitoring (CGM) machines are not suitable for all patients. To determine if these machines are safe and ideal for them, they should learn the basics of each. The following information can help current or potential users of insulin pumps and CGMs to conduct an informed conversation with their physician about their usage.

Historical Background

“In the early 1960s, Dr. Arnold Kadish developed the first insulin pump, which was the size of a Marine backpack. Over the years, insulin pumps have become much more refined and have decreased in bulk to the size and weight of a small pager. Insulin pump therapy, also known as continuous subcutaneous insulin infusion, is no longer seen as experimental and controversial, but rather is viewed as an acceptable alternative to multiple daily injection (MDI) therapy in the management of insulin-dependent diabetes.”1

Defining Insulin Pumps and CGMs

Insulin Pumps and CGMs are small and portable machines that help keep control over blood glucose levels. Specialists recommend them to patients who lack insulin or have resistance to it. 

Users frequently talk about the positive effects on their health condition. Both gadgets help decrease glycated hemoglobin and blood sugar levels. In certain cases, users have reached similar blood sugar levels to those of non-diabetic patients.

How do Insulin Pumps and CGMs work?

“Insulin pump treatment reduces the frequency of severe hypoglycemia compared with multiple daily injections treatment. The addition of a continuous glucose monitor (CGM), so-called sensor-augmented pump (SAP) treatment, has the potential to further limit the duration and severity of hypoglycemia as the system can detect and, in some systems, act on impending and prevailing low blood glucose levels. In this review we define SAP as an insulin pump with a CGM sensor that transmits the glucose readings to the insulin pump. There are currently 2 generations of SAPs on the market: in the first, the insulin dosing software operates independently of the CGM values so that the user has to make basal rate adjustments manually; in the second, the insulin dosing software and the CGM values are coupled which allows for automated suspension of basal insulin delivery in response to a predicted or detected low glucose level. For both SAP generations, however, meal and correction insulin delivery must be manually controlled, preferentially supported by the use of the insulin pump bolus calculator software.”2 

Insulin Pumps Basics

“The insulin pump is an electromechanical device that mimics the body’s natural insulin secretion from pancreatic β-cells by subcutaneously delivering rapid-acting insulin both at preset continuous basal rates and in extra bolus doses at mealtimes on demand. Insulin pumps allow for up to 24 different hourly basal rates in a 24-hour period. For bolus doses, pump users input their current blood glucose level and the number of carbohydrates they will consume, and the pump customizes their dose based on insulin currently on board (i.e., the remaining active insulin from the previous dose), their individualized insulin-to-carbohydrate ratio, and their individualized insulin sensitivity factor (i.e., their expected drop in blood glucose from 1 unit of insulin). Thus, insulin pumps are able to deliver insulin in a more physiological manner than other injection-based insulin regimens.”3

Insulin Pumps periodically administer a minimum amount of insulin to the patient, using a type that immediately evokes a response on the body. This appliance sends insulin through a long and slim hollow cylinder from the machine into the midriff. Insulin pumps attach to electronically powered gadgets that can record blood sugar levels. Depending on the type of insulin pump, users could maximize the amount of insulin that they receive when blood glucose levels rise. 


Pump Therapy
Pump Therapy (4)


“Pump therapy entails infusion of short-acting insulin (typically NovoRapid or Humalog) from a reservoir within the pump via plastic tubing into a fine-bore cannula placed in the subcutaneous tissue. The cannula is typically sited on the abdominal wall although other areas can also be used, and needs to be changed every 3 days. The cannula can be inserted by hand or by utilizing a purpose-designed device. In most models, the needle component of the cannula is removed after insertion, leaving a very fine plastic tube sitting in the subcutaneous tissues. CSII (continuous subcutaneous insulin infusion therapy) delivers insulin in two patterns: a pre-programmed continuous background insulin infusion (the rate usually varies over the 24-h period), with additional insulin boluses for food or to correct hyperglycemia. People using CSII do not take any additional long-acting insulin: both background and bolus insulin are delivered by the pump. The basal infusion rates are pre-programmed by the patient or his/her diabetes specialist but can be adjusted by the touch of a button. Basal insulin will continue to run until the insulin cartridge is empty. Insulin boluses are delivered as required under the patient’s direction; most pumpers make use of an inbuilt ‘bolus calculator’, which utilizes known variables for that individual (insulin: carbohydrate ratio, insulin sensitivity, and target blood glucose range) in conjunction with situation-specific data (current capillary glucose level, estimated carbohydrate intake and time since last insulin bolus). The pump and tubing can be removed for up to 1 h leaving the cannula in situ, for example for swimming, bathing or contact sports, such as boxing or rugby. Some pumps are waterproof and, therefore, can be kept on for prolonged aquatic pursuits.”5

CGMs Basics

CGM machines serve to track glucose levels at regular intervals. The machine notifies when blood sugar numbers experience abnormal changes and reports glucose levels in the screen thanks to a discrete sensor attached to the midriff area. The notification sound indicates that the user needs more insulin or should consume more carbs.


Continuous glucose monitoring systems (CGMS)
“Continuous glucose monitoring systems (CGMS). (A) Dexcom SEVEN® Plus, (B) Dexcom G4TM, (C) Guardian REAL-time, (D) FreeStyle Navigator®, (E) FreeStyle Navigator II, (F) HG1-c and (G) GlucoTrackTM.”5


What is the Downside of Owning Insulin Pumps and CGM Machines?

The benefits of these gadgets include the ability to check and control blood sugar levels. Therefore, they can minimize the consequences of abnormal glucose values.

The downside of these machines is their cost, as they are expensive to afford and maintain on a regular basis. The physician should know the users’ financial boundaries before choosing these gadgets since the insurance frequently does not cover these monitors.

For users who can afford these gadgets, learning how to properly manage them could still be confusing. Some users might experience difficulties using either insulin pumps or CGM machines, which could delay the treatment or lead to dosage errors.

“People using CSII (continuous subcutaneous insulin infusion therapy) do not take any additional long-acting insulin. Therefore, any interruption to insulin delivery from the pump (e.g. if the tubing has an air block or the cannula is kinked or dislodged) results in immediate insulin deficiency. Hyperglycemia and DKA (Diabetic ketoacidosis) can develop quickly, unless the problem is identified and rectified, for example by re-siting the cannula, refilling the insulin reservoir, changing the tubing, or by starting alternative insulin, such as an intravenous infusion. Technical problems with the pumps can occur; the pump manufacturing companies offer round-the-clock telephone support and are typically able to provide a replacement pump within 24 h if required. All patients using pumps are advised to retain a supply of their pre-pump insulin for use in an emergency situation, for example, in case of pump failure or damage.”8 

The importance of making informed decisions

After conducting careful research, users may offer an informed opinion to their physician about the use of these gadgets. Another useful tip is to read the product’s general attributes before discussing it with an expert. After a conversation in which both parties understand the terms, the physician will be determine if these gadgets are ideal, based on affordability, accessibility and the general impact it will have on the patient’s health status.

The contrast between SAP therapy and CGMs

“The benefit of using CGMs is clearly evident from sensor augment pump (SAP) therapy, which involves the combining of CGMs with the insulin pump. It demonstrated a significant reduction in HbA1c level, improvement of glycemic control and critically reduced severe hypoglycemic and hyperglycemic events in patients with type 1 diabetes mellitus in a rapid, sustainable and safe manner. The type 1 diabetics, who had a high HbA1c level and were older at diagnosis and randomization, experienced the most benefit from SAP therapy. The subjects treated by SAP therapy for 12 months reported significantly less hospitalization, increased treatment satisfaction and reduced fear of hypoglycemia. It was further demonstrated that the beneficial effects of SAP therapy persist, even after 36 months of its start. The HbA1c level decreased from 8.7% to 7.3% from the time when the SAP therapy was started to the end of 36 months (p < 0.0001). A study demonstrated that the initiation of CGMs before subcutaneous insulin infusion increases the CGMs frequency use in type 1 diabetes mellitus patients and significantly reduces the time spent in hypoglycemia.”9  

Insulin Pumps and CGMs, as alternatives to battle diabetes, still have pending work. “Diabetes has become a global epidemic during the last two decades. It is increasing at an alarming pace of 7.8 million new diabetics each year and is taking an unsustainable economic toll, amounting to 11.6% of the total healthcare expenditure. The ongoing research efforts to find the cure for diabetes by developing an artificial pancreas or by islet cell transplantation will take a lot of time based on the challenges involved and only a very limited scope for success. The current use of intensive insulin treatment is inadequate, as it leads to a marked increase in episodes of severe hypoglycemia. Moreover, insulin treatment is not expected to dramatically reduce the formation of Amadori products, which have a major impact on secondary health problems. Therefore, more frequent glucose monitoring is the only way to effectively manage diabetes by sustaining the physiological blood glucose level.”10

Insulin Pumps and CGMs cannot control diabetes on their own; patients need to follow adequate diets and exercise regimes for a healthy living. Ask a specialist for detailed instructions and advice before using these devices.  



(1, 3) Insulin Pump Class: Back to the Basics of Pump Therapy. Wilson Reece, S. & Hamby Williams, C.L. Diabetes Spectrum. 2014. 

(2) Sensor-Augmented Insulin Pumps and Hypoglycemia Prevention in Type 1 Diabetes. Steineck, I., Ranjan, A., Nørgaard, K. & Schmidt, S. Journal Of Diabetes Science and Technology. 2016. 

(4, 5, 8) Insulin pumps in hospital: a guide for the generalist physician. Evans, K. Clinical Medicine. 2014. 

(6, 7, 9, 10) Continuous Glucose Monitoring Systems: A Review. Kumar Vashist, S. Diagnostics. 2013. 


María Laura Márquez
13 October, 2018

Written by

María Laura Márquez, general doctor graduated from The University of Oriente in 2018, Venezuela. My interests in the world of medicine and science, are focused on surgery and its breakthroughs. Nowadays I practice my more:

3 thoughts on “Insulin Pumps and CGMs Basics

  1. Howdy I am so thrilled I found your webpage, I really found
    you by accident, while I was browsing on Bing for something else, Anyways I am
    here now and would just like to say kudos for a fantastic post and a all round entertaining blog (I also love the theme/design),
    I don’t have time to go through it all at the minute but I have book-marked it and also added in your RSS feeds, so when I have time I will be back to read more,
    Please do keep up the fantastic job.

  2. Hello! I know this is somewhat off topic but I was
    wondering which blog platform are you using for this site?
    I’m getting fed up of WordPress because I’ve had problems with hackers and I’m looking at alternatives for
    another platform. I would be fantastic if you
    could point me in the direction of a good platform.

Leave a Reply to Wm Saperstein Cancel reply

If you would also like a response sent to your email please add it in the email box below.