A1C: What It Is, Why It Matters to Contain Diabetes Costs

Hope Warshaw
May 3, 2018

What is Hemo­glo­bin A1C?

Hemo­glo­bin A1C is the part of red blood cells respon­si­ble for car­ry­ing oxy­gen to all cells of the body. In all cells glu­cose attach­es to hemo­glo­bin. Hemo­glo­bin A1C may also be referred to as HbA1C, A1C or gly­cat­ed hemo­glo­bin. Today, its most com­mon­ly called A1C.1

What is the A1C test and what does it mea­sure?

The A1C test mea­sures the over­all con­trol of glu­cose lev­els over the last three months. Think of it as a 24/7 video of all of the ups, downs and in between of glu­cose lev­els over this peri­od of time.

A1C is used to mea­sure glu­cose con­trol over time. This is pos­si­ble because the more glu­cose there is in the blood­stream, the more glu­cose attach­es to hemo­glo­bin in the cells. When peo­ple with dia­betes mea­sure their glu­cose with a blood glu­cose mon­i­tor or con­tin­u­ous glu­cose mon­i­tor, these results show their glu­cose lev­el at that one point in time, not over a peri­od of time. The use of A1C along with day to day glu­cose results should be used in tan­dem to man­age dia­betes and progress or change a man­age­ment plan.

A1C has a strong cor­re­la­tion to the devel­op­ment of dia­betes com­pli­ca­tions. Research has shown time and again that keep­ing A1C lev­els under con­trol over the years; the more like­ly it is that dia­betes com­pli­ca­tions can be pre­vent­ed or delayed.

How is A1C result report­ed?

A1C is report­ed as a per­cent­age. An exam­ple is 7.5%.

What’s the rec­om­mend­ed A1C for peo­ple with dia­betes?

The Amer­i­can Dia­betes Asso­ci­a­tion (ADA) rec­om­mends an A1C goal of <7% in most adults (not preg­nant), how­ev­er some health­care providers may rec­om­mend an A1C of <6.5% if the goal can be achieved and main­tained with­out adverse effects or events, such as fre­quent hypo­glycemia.2 On the con­verse an A1c of <8% is thought to be appro­pri­ate for peo­ple with a his­to­ry of hypo­glycemia (low glu­cose lev­els), lim­it­ed life expectan­cy, advanced com­pli­ca­tions or oth­er com­plex­i­ties of life.2

How often should A1C be mea­sured in peo­ple with dia­betes?

The ADA rec­om­mends that peo­ple who are meet­ing their treat­ment goals and have sta­ble glu­cose con­trol get their A1C checked at least two times a year. Peo­ple who are not meet­ing their treat­ment goals should have their A1c checked quar­ter­ly.2

Is there a rela­tion­ship between A1C and glu­cose con­trol?


This table shows how to relate an A1C test result to an esti­mate of aver­age glu­cose lev­els. Under­stand­ing this rela­tion­ship can help peo­ple and their providers set real­is­tic glu­cose tar­gets based on their A1C goals. The last col­umn shows that each A1C result has a large range, for exam­ple, an A1C of 7.0% may be clos­er to an esti­mat­ed aver­age glu­cose of 123, where­as an A1C of 7.9% may be clos­er to 180.2,3

Relate A1c Results to Glu­cose Lev­els

A1c (%) Esti­mat­ed Aver­age Glu­cose (mg/dL) Glu­cose Lev­els Between (mg/dL)
5 97 N/A
6 126 100 – 152
7 154 123 – 185
8 183 147 – 217
9 212 170 – 249
10 240 193 – 282
11 269 217 – 314
12 298 240 – 347

Is the A1C test accu­rate for every­one?

The A1C test has been avail­able for about 40 years and it has become, along with self-glu­cose mea­sures, a com­mon way for peo­ple and their providers to fol­low over­all glu­cose con­trol over the past three months. How­ev­er, in the last sev­er­al years two ques­tions have been raised about the poten­tial lim­i­ta­tions of A1C.

The first lim­i­ta­tion focus­es on accu­ra­cy. The A1C test may not be accu­rate for some peo­ple includ­ing peo­ple of African-Amer­i­can descent and peo­ple with liv­er and kid­ney dis­ease, some ane­mias and sick­le cell dis­ease.

The sec­ond lim­i­ta­tion is that while A1C offers an over­all pic­ture of glu­cose con­trol, it doesn’t pro­vide a detailed per­spec­tive. Glu­cose results, if in suf­fi­cient num­bers, show the dai­ly ups and downs and so-called pat­terns of glu­cose con­trol. More informed obser­va­tions and pos­si­ble treat­ment changes to a person’s care plan can be made more accu­rate­ly with both A1C and glu­cose results in hand.

There are an increas­ing num­ber of mobile apps and dig­i­tal health tools that help peo­ple track and ana­lyze their glu­cose results. BlueS­tar, pow­ered by Well­doc, is an FDA-cleared proven app for peo­ple with type 2 dia­betes that allows peo­ple with type 2 dia­betes to input their glu­cose results, com­mu­ni­cate with their provider on demand and much more.

Can A1C be used to diag­nose pre­di­a­betes and dia­betes?


Since 2010 ADA has endorsed the use of the A1C test to diag­nose pre­di­a­betes and dia­betes.4 It has some advan­tages, such as greater con­ve­nience and less day-to-day vari­a­tion of point in time glu­cose val­ues. It also has sev­er­al dis­ad­van­tages, one being low­er sen­si­tiv­i­ty.

The table pro­vides the A1C lev­els at which pre­di­a­betes and dia­betes can be diag­nosed.1

Diag­no­sis A1c Lev­el
Non-dia­betes Below 5.7%
Pre­di­a­betes 5.7 – 6.4%
Dia­betes (type 1 or 2) 6.5% or above

Why is Keep­ing A1C in a healthy zone so impor­tant in dia­betes care?

Numer­ous stud­ies con­duct­ed over the last sev­er­al decades con­clude that achiev­ing and main­tain­ing A1C results with­in the desired range (see answer to What’s the rec­om­mend­ed A1C for peo­ple with dia­betes?) can help pre­vent and/or delay the com­mon and cost­ly com­pli­ca­tions of dia­betes. These include: high blood pres­sure, decreased cir­cu­la­tion, heart attacks, strokes, dimin­ished sight or blind­ness, nerve dam­age to one or more areas of the body and more.2

How Does Con­trol of A1C relate to cost of dia­betes care?

The eco­nom­ic costs of dia­betes are stag­ger­ing. Recent­ly the ADA pub­lished the lat­est of their quin­quen­ni­al analy­ses. They showed total esti­mat­ed costs of $327 bil­lion with $237 bil­lion on direct costs and $90 bil­lion in indi­rect costs.5 For more details read this InsightsReflec­tions on the Stag­ger­ing 2017 Eco­nom­ic Cost of Dia­betes in U.S.

Data from numer­ous stud­ies show that bet­ter A1C demon­strates low­er total health­care costs. The intro­duc­tion to a recent study on the esti­mat­ed cost-effec­tive­ness of imple­ment­ing an inten­sive pro­gram of care for adults with type 2 dia­betes pro­vides a review of sev­er­al stud­ies.6 A study using claims data from a large health main­te­nance orga­ni­za­tion showed that the group of main­ly type 2 patients whose A1C was low­ered by 1% expe­ri­enced low­er total health care costs in the range of $685 to $950 less per year com­pared to peo­ple who had no A1C improve­ment. Anoth­er analy­sis from a large man­aged care orga­ni­za­tion showed that total dia­betes-relat­ed costs for peo­ple whose A1C was greater than 7% was $1,540 per patient dur­ing the 1-year fol­low-up. This was 32% high­er than the total dia­betes-relat­ed costs ($1,171) for peo­ple whose A1C was at or below 7%.

Recent­ly Tru­ven Health Ana­lyt­ics®, part of the IBM Wat­son Health™ busi­ness, con­duct­ed an analy­sis for Well­doc using the Mar­ketScan® Research Data­bas­es. These exten­sive data­bas­es include large employ­ers, man­aged care orga­ni­za­tions, hos­pi­tals, EMR providers and Medicare and Med­ic­aid pro­grams. Tru­ven uti­lized data from two ran­dom­ized con­trol tri­als show­ing BlueStar’s abil­i­ty to low­er and con­trol A1C by 1.7 to 2.0%.7,8 Tru­ven Health researchers cre­at­ed a com­plex cus­tom algo­rithm and applied it to the Mar­ketScan data, result­ing in quan­ti­fied total costs bro­ken down by A1C lev­els in a way that was com­pa­ra­ble between ages, sta­bil­i­ty and degree of glycemic con­trol. The data showed that the imple­men­ta­tion of BlueS­tar in a pop­u­la­tion of peo­ple with type 2 dia­betes can save, on aver­age, a range of $254 to $271 per user per month .9


  1. Sec­tion 1The A1C Test & Dia­betes. (Accessed April 25, 2018).
  2. Sec­tion 2American Dia­betes Asso­ci­a­tion. 6. Glycemic tar­gets: Stan­dards of Med­ical Care in Dia­betes -2018. Dia­betes Care.2018;41(Supp 1):S55-S64.
  3. Sec­tion 3National Gly­co­he­mo­glo­bin Stan­dard­iza­tion Pro­gram (NGSP). Har­mo­niz­ing Hemo­glo­bin A1c Test­ing. 2010 (Accessed April 25, 2018).
  4. Sec­tion 4American Dia­betes Asso­ci­a­tion. 2. Clas­si­fi­ca­tion and diag­no­sis of dia­betes: Stan­dards of Med­ical Care in Dia­betes -2018. Dia­betes Care.2018;41(Supp 1):S55-S64.
  5. Sec­tion 5American Dia­betes Asso­ci­a­tion. Eco­nom­ic Costs of Dia­betes in the U.S. in 2017. Dia­betes Care. 2018;41(5):917–928.
  6. Sec­tion 6Hirsch JD, et al. Esti­mat­ed Cost-Effec­tive­ness, Cost Ben­e­fit, and Risk Reduc­tion Asso­ci­at­ed with an Endocri­nol­o­gist-Phar­ma­cist Dia­betes Intense Med­ical Man­age­ment “Tune-Up” Clin­ic. J Man­ag Care Spec Pharm. 2017;23(3):318–326. (Accessed April 25, 2018)
  7. Sec­tion 7Quinn C, Shard­ell M, Ter­rin M, et al. Clus­ter-ran­dom­ized tri­al of mobile phone per­son­al­ized behav­ioral inter­ven­tion of blood glu­cose con­trol. Dia­betes Care 2011;34(9);1933–1943.
  8. Sec­tion 8Quinn C, Clough SS, Minor JM, et al. Well­docmobile dia­betes man­age­ment ran­dom­ized con­trolled tri­al: change in clin­i­cal and behav­ioral out­comes and patient and physi­cian sat­is­fac­tion. Dia­betes Tech­nol Ther 2008;10(3);160–168.
  9. Sec­tion 9Welldoc val­i­dates poten­tial of its dig­i­tal ther­a­peu­tic, BlueS­tar®, to sig­nif­i­cant­ly reduce health­care costs. (Accessed April 25, 2018).