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Diagnosis of

DiabetesNational Diabetes Information Clearinghouse

U.S. Departmentof Health and

Human Services

NATIONAL

INSTITUTESOF HEALTH

What is diabetes?Diabetes is a disease in which levels oblood glucose, also called blood sugar, areabove normal. People with diabetes haveproblems converting ood to energy. Nor-mally, ater a meal, the body breaks ooddown into glucose, which the blood carriesto cells throughout the body. Cells useinsulin, a hormone made in the pancreas,to help them convert blood glucose intoenergy.

People develop diabetes because thepancreas does not make enough insulin orbecause the cells in the muscles, liver, andat do not use insulin properly, or both.

As a result, the amount o glucose in theblood increases while the cells are starvedo energy. Over the years, high blood glu-cose, also called hyperglycemia, damagesnerves and blood vessels, which can leadto complications such as heart disease,stroke, kidney disease, blindness, nerveproblems, gum inections, and amputation.

Main Types of DiabetesThe two main types o diabetes are calledtype 1 and type 2. A third orm o diabetes

is called gestational diabetes.

Type 1 diabetes, ormerly calledjuvenile diabetes, is usually frstdiagnosed in children, teenagers, and

young adults. In this orm o diabe-tes, the pancreas no longer makes

insulin because the bodys immunesystem has attacked and destroyed thepancreatic cells specialized to makeinsulin. These insulinproducing cells

are called beta cells.Type 2 diabetes, ormerly called adult

onset diabetes, is the most commonorm. People can develop type 2diabetes at any age, even during child-hood. This orm o diabetes usuallybegins with insulin resistance, a condition in which muscle, liver, and atcells do not use insulin properly. As aresult, the body needs more insulin tohelp glucose enter cells to be used or

energy. At frst, the pancreas keepsup with the added demand by produc-ing more insulin. In time, however,the pancreas loses its ability to secreteenough insulin in response to meals.

Gestational diabetes is diabetes thatfrst occurs during pregnancy. When

women are pregnant, their need orinsulin appears to increase, and manycan develop gestational diabetesduring the late stages o pregnancy.

Although this orm o diabetes usu-

ally goes away ater the baby is born,a woman who has had it is more likelyto develop type 2 diabetes later in lie


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Other Types of DiabetesA number o other types o diabetes exist.A person may exhibit characteristics omore than one type. For example, inlatent autoimmune diabetes in adults(LADA), also called type 1.5 diabetes ordouble diabetes, people show signs o bothtype 1 and type 2 diabetes. Diagnosis usu-ally occurs ater age 30.

Most people with LADA still producetheir own insulin when frst diagnosed,

like those with type 2 diabetes, but withina ew years, they must take insulin tocontrol blood glucose levels. In LADA,as in type 1 diabetes, the beta cells o thepancreas stop making insulin becausethe bodys immune system attacks anddestroys them. Some experts believethat LADA is a slowly developing kind otype 1 diabetes.

Other types o diabetes include thosecaused by

genetic deects o the beta cell, suchas maturityonset diabetes o theyoung (MODY) and neonatal diabe-tes mellitus

genetic deects in insulin action,resulting in the bodys inability tocontrol blood glucose levels, as seenin leprechaunism and the RabsonMendenhall syndrome

diseases o the pancreas or conditionsthat damage the pancreas, such as

pancreatitis and cystic fbrosisexcess amounts o certain hor-

mones resulting rom some medicalconditionssuch as cortisol inCushings syndromethat workagainst the action o insulin

medications that reduce insulinaction, such as glucocorticoids, orchemicals that destroy beta cells

inections, such as congenital rubellaand cytomegalovirus

rare autoimmune disorders, such asstiman syndrome, an autoimmunedisease o the central nervous system

genetic syndromes associated withdiabetes, such as Down syndrome andPraderWilli syndrome

More inormation about MODY andneonatal diabetes mellitus is in theNational Diabetes Inormation Clear-inghouses act sheetMonogenic Forms

of Diabetes: Neonatal Diabetes Mel-litus and Maturityonset Diabetes of theYoung. The act sheet is available at

www.diabetes.niddk.nih.gov or bycalling 18008608747.

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Type 1 and Type 2DiabetesIn 1997, to move away rom namingthe two main types o diabetes basedon treatment or the age at onset, an

American Diabetes Association expertcommittee recommended universaladoption o simplifed terminology.The National Institute o Diabetesand Digestive and Kidney Diseases

(NIDDK) agrees.

Former NamePreferred

Name

Type I

juvenile diabetes

insulindependenttype 1diabetes

diabetes mellitus

IDDM

Type II

adultonset diabetesnoninsulindependent

type 2diabetes

diabetes mellitus

NIDDM

What is pre-diabetes?In prediabetes, blood glucose levels arehigher than normal but not high enoughor a diagnosis o diabetes. However,many people with prediabetes developtype 2 diabetes within 10 years. Expertsdisagree about the specifc blood glucoselevel they should use to diagnose diabetes,and through the years, that number haschanged. Individuals with prediabeteshave an increased risk o heart diseaseand stroke. With modest weight lossand moderate physical activity, people

with prediabetes can delay or preventtype 2 diabetes.


How are diabetes andpre-diabetes diagnosed?The ollowing tests are used or diagnosis:

A fasting plasma glucose (FPG) testmeasures blood glucose in a person

who has not eaten anything or atleast 8 hours. This test is used todetect diabetes and prediabetes.

An oral glucose tolerance test(OGTT) measures blood glucose

ater a person asts at least 8 hoursand 2 hours ater the person drinksa glucosecontaining beverage. Thistest can be used to diagnose diabetesand prediabetes.

A random plasma glucose test, alsocalled a casual plasma glucose test,measures blood glucose withoutregard to when the person beingtested last ate. This test, along withan assessment o symptoms, is usedto diagnose diabetes but not pre-diabetes.

Test results indicating that a person hasdiabetes should be confrmed with a sec-ond test on a dierent day.


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FPG TestThe FPG test is the preerred test ordiagnosing diabetes because o its conve-nience and low cost. However, it will misssome diabetes or prediabetes that canbe ound with the OGTT. The FPG testis most reliable when done in the morn-ing. Results and their meaning are shownin Table 1. People with a asting glucoselevel o 100 to 125 milligrams per deciliter(mg/dL) have a orm o prediabetes calledimpaired asting glucose (IFG). HavingIFG means a person has an increased risko developing type 2 diabetes but does nothave it yet. A level o 126 mg/dL or above,confrmed by repeating the test on anotherday, means a person has diabetes.

Table 1. FPG test

Plasma Glucose

Result (mg/dL) Diagnosis

99 or below Normal

100 to 125 Pre-diabetes(impaired fasting glucose)

126 or above Diabetes*

*Confrmed by repeating the test on a dierent day.

OGTTResearch has shown that the OGTT ismore sensitive than the FPG test or diag-nosing prediabetes, but it is less conve-nient to administer. The OGTT requiresasting or at least 8 hours beore the test.The plasma glucose level is measuredimmediately beore and 2 hours ater aperson drinks a liquid containing 75 gramso glucose dissolved in water. Results andtheir meaning are shown in Table 2. I theblood glucose level is between 140 and199 mg/dL 2 hours ater drinking the liq-uid, the person has a orm o prediabetescalled impaired glucose tolerance (IGT).Having IGT, like having IFG, means aperson has an increased risk o developingtype 2 diabetes but does not have it yet.

A 2hour glucose level o 200 mg/dL orabove, confrmed by repeating the test onanother day, means a person has diabetes.

Table 2. OGTT

2-hour Plasma

Glucose Result

(mg/dL) Diagnosis

139 or below Normal

140 to 199 Pre-diabetes (impairedglucose tolerance)

200 or above Diabetes*

*Confrmed by repeating the test on a dierent day.



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Gestational diabetes is also diagnosedbased on plasma glucose values measuredduring the OGTT, preerably by using100 grams o glucose in liquid or thetest. Blood glucose levels are checkedour times during the test. I blood glu-cose levels are above normal at least twiceduring the test, the woman has gestationaldiabetes. Table 3 shows the abovenormalresults or the OGTT or gestationaldiabetes.

Table 3. Gestational diabetes:Above-normal results for the OGTT*

Plasma Glucose Result

When (mg/dL)

Fasting 95 or higher

At 1 hour 180 or higher

At 2 hours 155 or higher

At 3 hours 140 or higher

Note: Some laboratories use other numbers or this test.*These numbers are or a test using a drink with 100 grams

o glucose.

Random Plasma Glucose TestA random, or casual, blood glucose levelo 200 mg/dL or higher, plus the presenceo the ollowing symptoms, can mean aperson has diabetes:

increased urination increased thirstunexplained weight loss

Other symptoms can include atigue,blurred vision, increased hunger, and sores

that do not heal. The doctor will check thepersons blood glucose level on anotherday using the FPG test or the OGTT toconfrm the diagnosis.

Additional inormation about thediagnosis and treatment o gestationaldiabetes is in the publication What

I need to know about GestationalDiabetes. This publication is availableatwww.diabetes.niddk.nih.gov or bycalling 18008608747.



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Who should be tested fordiabetes and pre-diabetes?The American Diabetes Associationrecommends that testing to detect pre-diabetes and type 2 diabetes be consid-ered in adults without symptoms whoare overweight or obese and have one ormore additional risk actors or diabetes.In those without these risk actors, test-ing should begin at age 45. The chart onpage 8 can be used to fnd out whether

someone is normal weight, overweight,obese, or extremely obese.

People aged 45 or older should considergetting tested or prediabetes or diabetes.People younger than 45 should considertesting i they are overweight, obese, orextremely obese and have one or more othe ollowing risk actors:

being physically inactivehaving a parent, brother, or sister with

diabetes

having a amily background that isArican American, Alaska Native,American Indian, Asian American,Hispanic/Latino, or Pacifc Islander

giving birth to a baby weighing morethan 9 pounds or being diagnosed

with gestational diabetes

having high blood pressure 140/90 mmHg or aboveor being treated or high blood pressure

having an HDL, or good, choles-terol level below 35 mg/dL or a trig-lyceride level above 250 mg/dL

having polycystic ovary syndrome,also called PCOS

having IFG or IGT on previous testing

having a condition called acanthosisnigricans, characterized by a dark,

velvety rash around the neck orarmpits

having a history o cardiovasculardiseasedisease aecting the heartand blood vessels

I results o testing are normal, testingshould be repeated at least every 3 years.Doctors may recommend more requenttesting depending on initial results andrisk status. People whose test resultsindicate they have prediabetes shouldhave their blood glucose checked againin 1 to 2 years and take steps to preventtype 2 diabetes.

When a woman is pregnant, the doctorwill assess her risk or developing gesta-tional diabetes at her frst prenatal visitand order testing as needed during thepregnancy. Women who develop gesta-tional diabetes should also have ollowup testing 6 to 12 weeks ater the baby isborn.



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In addition to weight, the location oexcess at on the body can be important.A waist measurement o 40 inches or moreor men or 35 inches or more or women islinked to insulin resistance and increases apersons risk or type 2 diabetes.

What steps can delay orprevent type 2 diabetes?

A major research study, the Diabetes Pre-vention Program (DPP), confrmed that

people with IGTprediabeteswereable to sharply reduce their risk o devel-oping diabetes during the study by losing5 to 7 percent o their body weight throughdietary changes and increased physicalactivity. Study participants ollowed a lowat, lowcalorie diet and engaged in regu-lar physical activity, such as walking brisklyor 30 minutes, fve times a week. Thesestrategies worked well or both men and

women and were especially eective orparticipants aged 60 and older.

More inormation about insulin resis-tance, the DPP, or how to lower riskor type 2 diabetes is available in theollowing publications:

Insulin Resistance and PrediabetesDiabetes Prevention Program

(DPP)

Am I at Risk for Type 2 Diabetes?These publications are available at

www.diabetes.niddk.nih.gov or bycalling 18008608747.

The National Diabetes EducationProgram (NDEP) oers severalbooklets as part o its Small Steps,Big Rewards campaign on preventingtype 2 diabetes, including inormationabout setting goals, tracking progress,implementing a walking program,and fnding additional resources.These materials are available at

www.ndep.nih.gov or by calling theNDEP at 1888693NDEP (6337).



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How is diabetes managed?People with diabetes can manage it withmeal planning, physical activity, and, ineeded, medications. Additional inor-mation about taking care o type 1 ortype 2 diabetes is available in the publica-tion Your Guide to Diabetes: Type 1 andType 2. This publication is available at

www.diabetes.niddk.nih.gov or by calling18008608747.

Points to RememberDiabetes, prediabetes, and gesta-

tional diabetes are diagnosed bychecking blood glucose levels.

Tests used or diagnosing diabe-tes and prediabetes include theasting plasma glucose (FPG) testand the oral glucose tolerance test(OGTT).

People aged 45 or older shouldconsider getting tested or pre-diabetes or diabetes. People

younger than 45 who are over-weight, obese, or extremely obeseand have one or more additionalrisk actors or diabetes shouldconsider testing.

Many people with prediabetesdevelop type 2 diabetes within10 years.

People with prediabetes candelay or prevent type 2 diabetesby losing a modest amount o

weight through regular physicalactivity and a diet low in at andcalories.

Hope through ResearchThe NIDDK conducts and supportsresearch related to the causes, treatment,and prevention o diabetes.

Participants in clinical trials can play amore active role in their own health care,gain access to new research treatmentsbeore they are widely available, and helpothers by contributing to medical researchFor inormation about current studies,

visitwww.ClinicalTrials.gov.



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For More InformationAmerican Association of DiabetesEducators200 West Madison Street, Suite 800Chicago, IL 60606Phone: 18003383633 or 3124242426Diabetes Educator Access Line:

1800TEAMUP4 (8326874)Fax: 3124242427Email: [email protected]: www.diabeteseducator.org

American Diabetes Association1701 North Beauregard Street

Alexandria, VA 22311Phone: 1800DIABETES (3422383)Fax: 7035496995Email: [email protected]: www.diabetes.org

Juvenile Diabetes Research FoundationInternational120 Wall StreetNew York, NY 100054001Phone: 1800533CURE (2873)Fax: 2127859595Email: [email protected]: www.jdr.org

National Diabetes Education Program1 Diabetes WayBethesda, MD 208149692Phone: 1888693NDEP (6337)TTY: 18665691162Fax: 7037384929Email: [email protected]: www.ndep.nih.gov



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You may also fnd additional inormation about thistopic by visiting MedlinePlus atwww.medlineplus.gov.

This publication may contain inormation about med-ications. When prepared, this publication includedthe most current inormation available. For updatesor or questions about any medications, contactthe U.S. Food and Drug Administration toll-ree at1888INFOFDA (4636332) or visitwww.fda.gov.Consult your doctor or more inormation.

National DiabetesInformation Clearinghouse

1 Information WayBethesda, MD 208923560Phone: 18008608747TTY: 18665691162Fax: 7037384929Email: [email protected]: www.diabetes.niddk.nih.gov

The National Diabetes InformationClearinghouse (NDIC) is a service of the

National Institute of Diabetes and Digestiveand Kidney Diseases (NIDDK). The NIDDKis part of the National Institutes of Health ofthe U.S. Department of Health and HumanServices. Established in 1978, the Clearinghouseprovides information about diabetes to peoplewith diabetes and to their families, healthcare professionals, and the public. The NDICanswers inquiries, develops and distributespublications, and works closely with professionaland patient organizations and Governmentagencies to coordinate resources about diabetes.

Publications produced by the Clearinghouse arecarefully reviewed by both NIDDK scientists andoutside experts. This publication was reviewedby David Harlan, M.D., NIDDK.

This publication is not copyrighted. The Clearinghouseencourages users o this act sheet to duplicate anddistribute as many copies as desired.

This act sheet is also available atwww.diabetes.niddk.nih.gov.

U.S. DEPARTMENT OF HEALTH

AND HUMAN SERVICES

National Institutes of Health

NIH Publication No. 094642

O t b 2008

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