How to read an Indian blood sugar lab report

An Indian pathology report usually carries some combination of five lines. They are not five versions of the same test — they measure genuinely different things, and mixing them up is the single most common reason people misread their own report.

FBS — fasting blood sugar

Blood taken after at least eight hours with no food and no sugary drinks. Water is fine. This is the value the fasting thresholds refer to. If you had chai with sugar at 6 a.m. and gave blood at 8 a.m., the number on the page is not a fasting value, whatever the report calls it.

PPBS — post-prandial blood sugar

Blood taken two hours after a meal, timed from the first bite rather than the last. This is not the same test as the two-hour value in an oral glucose tolerance test, even though both are described as "2 hours" and both are often compared against the same 140 and 200 mg/dL figures. The OGTT uses a standardised 75 g glucose drink so that everyone is challenged identically. A PPBS after home food depends on what was on the plate, so the same person can produce very different numbers on different days.

RBS — random blood sugar

Blood taken at any time, with no reference to meals. It is a screening measurement. A random value of 200 mg/dL or above together with the classic symptoms of high blood glucose is one of the published criteria for diabetes; a random value on its own, without symptoms, is a reason for a proper fasting test rather than a conclusion.

OGTT — oral glucose tolerance test

Fasting blood is taken, you drink a measured 75 g glucose solution, and blood is taken again at two hours. It is the most demanding of the tests to sit through and the most standardised. It is also the test that finds a particular group of people whose fasting value looks acceptable but whose two-hour value does not — a pattern that appears to be relatively common in South Asians.

HbA1c

Not a blood sugar reading at all. It measures the proportion of your haemoglobin that has glucose stuck to it, which reflects average glucose over roughly the previous two to three months. It needs no fasting and no timing. What it can and cannot tell you is its own page.

Units: mg/dL and mmol/L

Indian labs almost always report mg/dL. UK, Australian, Canadian and most European labs report mmol/L. To convert, divide mg/dL by 18. A fasting value of 126 mg/dL is 7.0 mmol/L — the same threshold written two ways. The full conversion table is here.

Why the lab's "normal range" column may differ

The reference interval printed beside your result is set by the laboratory. It may follow WHO, it may follow ADA, it may be inherited from an analyser manufacturer, and it may not have been reviewed recently. That is why the same 105 mg/dL fasting result can be flagged on one report and not on another — the ADA places the lower edge of prediabetes at 100 mg/dL, WHO at 110 mg/dL. Both published sets are on the levels page.

The part this page cannot do

Interpret it. A report is read alongside your symptoms, your history, your medicines, your weight and often a repeat test. Published criteria explicitly require confirmation before a diagnosis is made. Take the report to a doctor — including, and especially, if a number on it frightened you.