Editing Blood glucose monitoring (section)

==Continuous glucose monitoring==
{{See also|Flash glucose monitoring}}
A [[continuous glucose monitor]] determines glucose levels on a continuous basis (every few minutes).<ref>{{cite journal |vauthors=Aussedat B, Dupire-Angel M, Gifford R, Klein JC, Wilson GS, Reach G | title = Interstitial glucose concentration and glycemia: implications for continuous subcutaneous glucose monitoring | journal = American Journal of Physiology. Endocrinology and Metabolism | volume = 278 | issue = 4 | pages = E716-28 | date = April 2000 | pmid = 10751207 | doi = 10.1152/ajpendo.2000.278.4.e716 | s2cid = 19509504 }}</ref> A typical system consists of:
* a disposable glucose sensor placed just under the skin, which is worn for a few days until replacement
* a link from the sensor to a non-implanted transmitter which communicates to a radio receiver
* an electronic receiver is worn like a pager (or insulin pump) that displays glucose levels with nearly continuous updates, as well as monitors rising and falling trends.<ref>{{Cite web |title=Continuous Glucose Monitoring {{!}} NIDDK |url=https://www.niddk.nih.gov/health-information/diabetes/overview/managing-diabetes/continuous-glucose-monitoring |access-date=2023-01-11 |website=National Institute of Diabetes and Digestive and Kidney Diseases |language=en-US}}</ref>

Continuous glucose monitors measure the concentration of glucose in a sample of [[interstitial fluid]].  Shortcomings of CGM systems due to this fact are:
* continuous systems must be calibrated with a traditional blood glucose measurement (using current technology) and therefore require both the CGM system and occasional "fingerstick"
* glucose levels in interstitial fluid lag behind blood glucose values
Patients, therefore, require traditional fingerstick measurements for calibration (typically twice per day) and are often advised to use fingerstick measurements to confirm hypo- or hyperglycemia before taking corrective action.

The lag time discussed above has been reported to be about 5 minutes.<ref>{{cite journal | vauthors = Wentholt IM, Vollebregt MA, Hart AA, Hoekstra JB, DeVries JH | title = Comparison of a needle-type and a microdialysis continuous glucose monitor in type 1 diabetic patients | journal = Diabetes Care | volume = 28 | issue = 12 | pages = 2871–6 | date = December 2005 | pmid = 16306547 | doi = 10.2337/diacare.28.12.2871 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Steil GM, Rebrin K, Mastrototaro J, Bernaba B, Saad MF | title = Determination of plasma glucose during rapid glucose excursions with a subcutaneous glucose sensor | journal = Diabetes Technology & Therapeutics | volume = 5 | issue = 1 | pages = 27–31 | year = 2003 | pmid = 12725704 | doi = 10.1089/152091503763816436 }}</ref><ref>{{cite journal | vauthors = Wilhelm B, Forst S, Weber MM, Larbig M, Pfützner A, Forst T | title = Evaluation of CGMS during rapid blood glucose changes in patients with type 1 diabetes | journal = Diabetes Technology & Therapeutics | volume = 8 | issue = 2 | pages = 146–55 | date = April 2006 | pmid = 16734545 | doi = 10.1089/dia.2006.8.146 }}</ref>  Anecdotally, some users of the various systems report lag times of up to 10–15 minutes. This lag time is insignificant when blood sugar levels are relatively consistent. However, blood sugar levels, when changing rapidly, may read in the normal range on a CGM system while in reality the patient is already experiencing symptoms of an out-of-range blood glucose value and may require treatment. Patients using CGM are therefore advised to consider both the absolute value of the blood glucose level given by the system as well as any trend in the blood glucose levels. For example, a patient using CGM with a blood glucose of 100&nbsp;mg/dl on their CGM system might take no action if their blood glucose has been consistent for several readings, while a patient with the same blood glucose level but whose blood glucose has been dropping steeply in a short period of time might be advised to perform a fingerstick test to check for hypoglycemia.{{cn|date=February 2024}}

Continuous monitoring allows examination of how the blood glucose level reacts to insulin, exercise, food, and other factors. The additional data can be useful for setting correct [[insulin]] dosing ratios for food intake and correction of hyperglycemia. Monitoring during periods when blood glucose levels are not typically checked (e.g. overnight) can help to identify problems in insulin dosing (such as basal levels for insulin pump users or long-acting insulin levels for patients taking injections). Monitors may also be equipped with alarms to alert patients of hyperglycemia or hypoglycemia so that a patient can take corrective action(s) (after fingerstick testing, if necessary) even in cases where they do not feel symptoms of either condition. While the technology has its limitations, studies have demonstrated that patients with continuous sensors experience a smaller number of hyperglycemic and hypoglycemic events, a reduction in their [[glycated hemoglobin]] levels and a decrease in glycemic variability.<ref>{{Cite journal|last=Hirsch|first=Irl B.|date=August 2015|title=Glycemic Variability and Diabetes Complications: Does It Matter? Of Course It Does!|journal=Diabetes Care|language=en|volume=38|issue=8|pages=1610–1614|doi=10.2337/dc14-2898|pmid=26207054|issn=0149-5992|doi-access=free}}</ref><ref>{{cite journal | vauthors = Garg S, Zisser H, Schwartz S, Bailey T, Kaplan R, Ellis S, Jovanovic L | title = Improvement in glycemic excursions with a transcutaneous, real-time continuous glucose sensor: a randomized controlled trial | journal = Diabetes Care | volume = 29 | issue = 1 | pages = 44–50 | date = January 2006 | pmid = 16373894 | doi = 10.2337/diacare.29.01.06.dc05-1686 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Deiss D, Bolinder J, Riveline JP, Battelino T, Bosi E, Tubiana-Rufi N, Kerr D, Phillip M | s2cid = 27141532 | title = Improved glycemic control in poorly controlled patients with type 1 diabetes using real-time continuous glucose monitoring | journal = Diabetes Care | volume = 29 | issue = 12 | pages = 2730–2 | date = December 2006 | pmid = 17130215 | doi = 10.2337/dc06-1134 | doi-access = free }}</ref><ref>{{cite journal |vauthors= Mastrototaro JJ, Cooper KW, Soundararajan G, Sanders JB, Shah RV |title=Clinical experience with an integrated continuous glucose sensor/insulin pump platform: A feasibility study |journal=Advances in Therapy |date=Sep–Oct 2006 |volume=23 |issue=5 |pages=725–732 |doi=10.1007/BF02850312 |pmid=17142207|s2cid=34836239 }}</ref><ref>{{cite journal | vauthors = Garg S, Jovanovic L | title = Relationship of fasting and hourly blood glucose levels to HbA1c values: safety, accuracy, and improvements in glucose profiles obtained using a 7-day continuous glucose sensor | journal = Diabetes Care | volume = 29 | issue = 12 | pages = 2644–9 | date = December 2006 | pmid = 17130198 | doi = 10.2337/dc06-1361 | doi-access = free }}</ref> Compared to intermittent testing, it is likely to help reduce hypertensive complications during pregnancy.<ref>{{cite journal | vauthors = Jones LV, Ray A, Moy FM, Buckley BS | title = Techniques of monitoring blood glucose during pregnancy for women with pre-existing diabetes | journal = The Cochrane Database of Systematic Reviews | volume = 5 | pages = CD009613 | date = May 2019 | issue = 6 | pmid = 31120549 | pmc = 6532756 | doi = 10.1002/14651858.CD009613.pub4 | collaboration = Cochrane Pregnancy and Childbirth Group }}</ref> In a recent systematic review with meta-analysis  about glycaemia monitoring in critical patients<ref>{{cite journal |last1=Arias-Rivera |first1=S |title=Blood glucose monitoring in critically ill adult patients: type of sample and method of analysis. Systematic review and meta-analysis |journal=Enfermeria Intensiva |date=2024 |volume=35 |issue=1 |pages=45–72 |doi=10.1016/j.enfie.2023.02.002 |pmid=37474427 |url=https://www.sciencedirect.com/science/article/pii/S2529984023000344|doi-access=free }}{{Creative Commons text attribution notice|cc=by4|from this source=yes}}</ref> who are haemodynamically unstable and require intensive monitoring of glycaemia it concluded that should be undertaken using arterial blood samples and POC blood gas analysers, as this is more reliable and is not affected by the variability of different confusion factors. Determining glycaemia in capillary blood using glucometry may be suitable in stable patients or when close monitoring of glycaemia is not required.

Continuous blood glucose monitoring is not automatically covered by [[health insurance]] in the United States in the same way that most other diabetic supplies are covered (e.g. standard glucose testing supplies, [[insulin]], and [[insulin pump]]s). However, an increasing number of insurance companies do cover continuous glucose monitoring supplies (both the receiver and disposable sensors) on a case-by-case basis if the patient and doctor show a specific need. The lack of insurance coverage is exacerbated by the fact that disposable sensors must be frequently replaced. Some sensors have been U.S. [[Food and Drug Administration]] (FDA) approved for 7- and 3-day use, (although some patients wear sensors for longer than the recommended period) and the receiving meters likewise have finite lifetimes (less than 2 years and as little as 6 months). This is one factor in the slow uptake in the use of sensors that have been marketed in the United States.{{citation needed|date=April 2022}}

The principles, history and recent developments of operation of electrochemical glucose biosensors are discussed in a chemical review by [[Joseph Wang]].<ref>{{cite journal | vauthors = Wang J | s2cid = 9105453 | title = Electrochemical glucose biosensors | journal = Chemical Reviews | volume = 108 | issue = 2 | pages = 814–25 | date = February 2008 | pmid = 18154363 | doi = 10.1021/cr068123a }}</ref>