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Type 2 Diabetes: Investigations and Monitoring with blood and urine tests
Scope
Non-fasting blood tests are usually sufficient to monitor lipids
Out of scope
Although some GPs measure FBC, LFTs, B12 and folate there is not a good evidence base for doing this routinely. Rarely an unexpected drop in HbA1c will be due to anaemia. Liver transaminases (ALT or AST) should be measured prior to starting a statin, and again after 3 and 12 months. Long term monitoring of LFTs is not indicated.
In Type 2 Diabetes it is appropriate to measure TSH once at diagnosis, however annual TSH measurement is not recommended because the incidence of new hypothyroidism is low. (This differs from Type 1 Diabetes where annual testing is recommended).
Vitamin B12 levels may be reduced in patients on metformin. However the clinical significance is uncertain and we do not advocate screening for this.
This guidance does not cover other aspects of diabetes monitoring such as retinal screening and foot examination.
Differential Diagnoses
HbA1C: In symptomatic patients diagnosis of diabetes is based on one reading of greater than 48. In asymptomatic patients there needs to be 2 consecutive readings greater than 48 mmol/mol. If the second result is lower than 48 this value should be used in preference, the patient categorised as high risk and the HbA1c repeated in one year. For monitoring a minimum of 30 days for repeat testing is recommended.
For more detailed information see
Exeter Diabetes Handbook
At Diagnosis
- Blood - FBC, Renal, ALT or LFT if single test not available, HbA1C, non-fasting lipid profile (total cholesterol, HDL cholesterol, non-HDL cholesterol and triglycerides), TSH
- Urine - Albumin : Creatinine Ratio
Annually
- Blood - Renal, HbA1C, non-HDL cholesterol (non-fasting)
- Urine: Albumin : Creatinine Ratio
Every 6 months
- HbA1c
Limitations of HbA1c
- Rapid onset of diabetes – an increase in HbA1c may not be detected until a few weeks later
- Suspected type 1 diabetes – rapid onset of symptoms, weight loss, ketosis
- Children - because most will have type 1 diabetes
- Steroids - Antipsychotics & immunosuppressants can raise blood glucose, rarely recipitously
- After pancreatitis or pancreatic surgery
- Pregnancy. Multiple factors make HbA1c lower in pregnancy
- Conditions with reduced red cell survival may lower HbA1c markedly
- Haemoglobinopathy which will normally be detected by the lab, but should be suspected in racial groups where there is a high prevalence of sickle trait, sickle disease or thalassaemia
- Haemolytic anaemia
- Severe blood loss
- Splenomegaly
- Antiretroviral drugs
- Increased red cell survival may increase HbA1c e.g. splenectomy
- Renal dialysis patients have a markedly reduced HbA1c especially if treated with erythropoietin
- Iron and B12 deficiency and their treatment. May raise or lower HbA1c
Evidence
NICE guideline: Type 2 diabetes in adults: management. [NG28] Published December 2015
Lipid modification: cardiovascular risk assessment and the modification of blood lipids for the primary and secondary prevention of cardiovascular disease. NICE guideline [CG181] Published: July 2014.
NICE guideline: Chronic kidney disease in adults: assessment and management [CG182] Published July 2014.
Pathway Group
This guideline has been signed off by the Pathology Optimisation Clinical Group on behalf of NHS Devon.
Publication date: June 2017
