Guidelines presents Primary Care Hacks, a series of clinical aide-memoires across a range of topics. Developed by Dr Kevin Fernando, Primary Care Hacks aim to provide a quick and easy resource for primary healthcare professionals and ultimately help improve patients' lives.
Take a Look at Medscape UK's other Primary Care Hacks
| Managing Abnormal Blood Test Results | Managing Cardiovascular Conditions | Managing Diabetes, Metabolic, and Endocrine Conditions |
|---|---|---|
Lifestyle Changes for Managing Hypertension DOAC Dosing for Stroke Prevention in Nonvalvular AF and Renal Impairment | Identification and Management of People with MASLD and MASH Extra-Glycaemic Indications of SGLT2 Inhibitors Comparison of ADA/EASD and NICE Recommendations on Managing Type 2 Diabetes Type 2 Diabetes Cardiovascular Renal Metabolic Review Checklist |
The Diagnosis and Classification of Diabetes in Primary Care
Latest UpdateNovember 2023: Pancreatic cancer diagnosis in type 3c diabetes updated to include recommendation from the Scottish referral guidelines for suspected cancer; useful resources added to provide information on steroid-induced diabetes. |
Type 1 and type 2 diabetes are the most commonly encountered types of diabetes in primary care, but there are a number other forms of diabetes that healthcare professionals need to be aware of. It is increasingly challenging to differentiate between types of diabetes in primary care; this Primary Care Hack summarises the diagnosis and classification of several different types of diabetes and offers diagnostic tips, as well as pitfalls to avoid when diagnosing diabetes in primary care.
Click on the link below for a downloadable PDF of the Primary Care Hack
The Diagnosis and Classification of Diabetes in Primary Care
Expand the table below for full view.
| T1D | LADA | T2D | Monogenic Diabetes | GDM | T3cD (Pancreatogenic) | |
|---|---|---|---|---|---|---|
Pathophysiology | Autoimmune destruction of pancreatic beta cells Clinical diagnosis ± PG and ketone levels. Urgent specialist discussion required It is increasingly challenging to differentiate T1D from T2D, partly due to the obesity epidemic. Often the safest strategy is to presume T1D until proven otherwise | LADA is essentially ‘slow-onset’ T1D Gradual autoimmune destruction of pancreatic beta cells. Diagnosis and management similar to T1D See Diabetes UK’s Latent autoimmune diabetes in adults | IR with relative insulin deficiency T2D is usually diagnosed when HbA1c ≥48 mmol/mol. If use of HbA1c is inappropriate (e.g. pregnant women, genetic variants [HbS or HbC trait], acute or chronic blood loss, end-stage kidney disease) then T2D is diagnosed by an FPG ≥7 mmol/l If asymptomatic, the diagnosis should never be based on a single abnormal HbA1c or PG level; at least one additional abnormal test is essential | Genetic mutation leading to diabetes. Most common is MODY See diabetesgenes.org for diagnosis guidance | Impaired glucose tolerance in pregnancy due to pancreatic beta-cell dysfunction on background of IR NICE NG3[1] diagnostic criteria: FPG ≥5.6 mmol/l or 2-hour PG post 75 g OGTT ≥7.8 mmol/l, i.e. much lower than the diagnostic criteria for non-pregnant individuals Some areas use FPG levels ≥5.1 mmol/l, as any degree of hyperglycaemia in pregnancy increases the risk of both adverse fetal and maternal outcomes | Diabetes associated with disease, trauma or surgery of the exocrine pancreas Causes include acute and chronic pancreatitis, pancreatic surgery, cystic fibrosis, haemochromatosis and pancreatic cancer See Pancreatic Cancer Action’s information on T3cD Often misdiagnosed as T2D |
Age at Diagnosis | Usually <25 years but can occur at any age | Can occur at any adult age Often initially mistaken for T2D | Both adults and children at any age | MODY onset often during 2nd to 5th decades and usually <45 years | Can occur in any women of child-bearing age Women with GDM have a nearly 10-fold higher risk of developing TD2[2] | Both adults and children at any age Exclude pancreatic cancer in those >60 years (NICE NG12)[3] or >55 years (Scottish referral guidelines for suspected cancer)[4] with new-onset diabetes and unexplained |
| Weight at Diagnosis | Usually underweight but occur at any weight Marked weight loss common | Variable | Usually overweight | Variable | RF for GDM include overweight/obesity but baseline weight can be variable | Variable |
Family History of Diabetes | Infrequent (5–10%) | Variable | Frequent (75–90%) | Multi-generational MODY is AD Strong FH of diabetes (any type) involving two or three consecutive generations may point towards a diagnosis of MODY | FH of diabetes is an important RF for GDM | Variable Haemochromatosis and CF are AR |
History of Autoimmune Disease | Often personal or FH, e.g. thyroid and coeliac disease | Variable | Variable | Variable | Variable | Variable but often PEI present, e.g. diarrhoea and steatorrhoea, abdominal discomfort, flatulence and bloating Check stool sample for faecal elastase-1. Low levels suggestive of PEI |
Pancreatic Autoantibodies | Present | Present | Absent | Absent | Absent | Absent |
C-peptide Levels | Low/absent | Initially normal then low/absent | Normal to high | Normal | Normal to high | Low |
Insulin Sensitivity | Normal when treated | Normal when treated | Reduced | Normal (maybe reduced if obese) | Reduced | Compensatory increase in peripheral insulin sensitivity |
Insulin Requirements | Immediate; specialist input urgently required | Immediate; specialist input urgently required | Variable | Variable | Variable | Variable Much more likely to need insulin within 5 years of diagnosis |
Risk of DKA | High | Low initially but high once insulin-deficient | Low but euglycaemic DKA is a rare side-effect of SGLT2i See the Guidelines Primary Care Hack, What Next After Metformin? | Low | Low | Low but hypoglycaemia is common and can be prolonged |
Commonly Used Drugs That Can Induce Hyperglycaemia or Cause Diabetes
| Useful Resources
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| Table based on Summaries of Product Characteristics and the author’s clinical experience and appraisal of the literature. | ||||||
| Abbreviations AD=autosomal dominant; AR=autosomal recessive; CF=cystic fibrosis; DKA=diabetic ketoacidosis; FH=family history; FPG=fasting plasma glucose; GDM=gestational diabetes mellitus; HbA1c=haemoglobin A1c; HbC=haemoglobin C; HbS=haemoglobin S; IR=insulin resistance; LADA=latent autoimmune diabetes in adults; MODY=maturity onset diabetes of the young; NG=NICE Guideline; OGTT=oral glucose tolerance test; PEI=pancreatic exocrine insufficiency; PG=plasma glucose; RF=risk factor(s); SGLT2i=sodium-glucose cotransporter-2 inhibitors; T1D=type 1 diabetes; T2D=type 2 diabetes; T3cD=type 3c diabetes. | ||||||
| This Primary Care Hack was developed by Dr Kevin Fernando, GP Partner, North Berwick Health Centre; GP with special interest in CVRM and medical education; Content Advisor for Medscape UK and Medscape Global. Primary Care Hacks are for information for primary healthcare professionals in the UK only. They bring together currently available recommendations and/or prescribing information and indications for therapeutics licensed within Great Britain. Licensed indications and/or prescribing information for Northern Ireland may differ. You are advised to review local licensed indications before prescribing any therapeutic. Primary Care Hacks are reviewed intermittently to ensure the information is up to date at the time of publication. Primary Care Hacks are independently produced by WebMD, LLC and have not been created in conjunction with any guideline or prescribing body. |