F. LIVER, VITAMIN, AND OTHER SUPPORTING TESTS
11. Liver Function Tests (LFTs)
What it measures: A blood panel checking liver enzymes (such as ALT and AST) and other markers of liver health.
Why it's needed: Several diabetes medications are processed by the liver or can rarely affect it (pioglitazone's class has a historical link to liver toxicity in an earlier drug; metformin is generally avoided in significant liver disease), and diabetes itself is strongly associated with fatty liver disease (metabolic dysfunction-associated steatotic liver disease, MASLD), so baseline and periodic monitoring helps catch problems early and guides medication choices.
How often: At diagnosis/baseline, and then periodically (roughly annually, or as directed) — particularly for anyone on pioglitazone or with risk factors for fatty liver disease, or if symptoms suggestive of liver problems develop.
12. Vitamin B12 (for long-term metformin users)
What it measures: Blood level of vitamin B12, a nutrient needed for nerve function and red blood cell production.
Why it's needed: Metformin reduces B12 absorption in the gut over time, and deficiency can develop gradually and silently, sometimes mimicking or worsening diabetic nerve symptoms (numbness, tingling) or causing fatigue and memory problems that are easy to misattribute to other causes.
How often: Baseline check reasonable when starting long-term metformin therapy, then periodically — commonly every 2 to 3 years, or annually for people at higher risk (strict vegetarian diet, older age, or symptoms suggestive of deficiency).
13. Thyroid Function (TSH)
What it measures: Thyroid-stimulating hormone, the main screening test for an underactive or overactive thyroid gland.
Why it's needed: Thyroid disease is significantly more common in people with type 1 diabetes (both conditions are autoimmune and often occur together) and is also more common in the general population with age, particularly among women; thyroid problems can also affect blood sugar control and be mistaken for other symptoms (fatigue, weight change).
How often: At diagnosis for type 1 diabetes and periodically thereafter (roughly every 1–2 years, or if symptoms develop); for type 2 diabetes, testing is generally based on symptoms, age, or other risk factors rather than routine annual screening, though practices vary.
14. Urinalysis (Routine Urine Test)
What it measures: A basic screening of urine for glucose, ketones, protein, blood, and signs of infection, in addition to the more specific UACR test described above.
Why it's needed: Can help detect urinary tract infections (more common in diabetes), ketones (important if blood sugar is very high or the person feels unwell, since this can signal a dangerous complication called diabetic ketoacidosis, more relevant in type 1 diabetes but possible in type 2 as well), and other abnormalities.
How often: At diagnosis and periodically as part of routine review, or specifically when symptoms (burning with urination, unexplained illness, very high blood sugar) suggest it is needed.