Infection Test

Dengue Test (NS1, IgM, IgG)

Name: Dengue Test (NS1, IgM, IgG): What Your Results Mean
Creator: Suman Konda
Published: 2026-07-05

Dengue fever is one of the most common mosquito-borne illnesses in tropical and subtropical regions. Three different blood tests are used to confirm it: here's what each one means.

Written and clinically reviewed by Suman Konda, PharmD, Clinical Pharmacist · Editorial policy · Not medical advice

Last reviewed and updated: 01 August 2026 · How we check our content

The three dengue tests explained

Dengue diagnosis depends on when you test after symptoms start. Different tests are positive at different times:

Test	When Positive	What it detects
NS1 Antigen	Day 1–5 of fever	The dengue virus itself (early detection)
IgM Antibody	Day 4–5 onwards	Your body's early immune response
IgG Antibody	Day 7+ / past infection	Past dengue infection or secondary infection

What does a POSITIVE NS1 mean?

POSITIVE NS1 Antigen: Active dengue infection

A positive NS1 antigen test in the first 5 days of fever confirms active dengue virus in your blood. NS1 is the most reliable test early in illness. A negative NS1 after day 5 does not rule out dengue: the virus clears quickly; by then, antibody tests (IgM) become more useful.

What does POSITIVE IgM mean?

POSITIVE IgM Antibody: Recent dengue infection

Positive IgM means your immune system has recently mounted a response to dengue: consistent with a current or very recent (within 3 months) infection. IgM becomes detectable from around day 4–5 and stays elevated for 2–3 months after recovery.

What does POSITIVE IgG mean?

POSITIVE IgG: Past infection or secondary dengue

IgG stays in your blood for life after dengue infection. A positive IgG alone means you had dengue in the past. IgG positive + IgM positive = secondary dengue infection (second time getting dengue). Secondary dengue is more likely to cause dengue haemorrhagic fever: watch for warning signs carefully.

Platelet count in dengue: when is it dangerous?

Platelet Count	What it means
> 150,000	Normal: monitor at home
50,000 – 150,000	Low: daily monitoring needed
20,000 – 50,000	Very low: hospital admission advised
< 20,000	Critical: platelet transfusion may be needed

Warning signs: go to hospital immediately if you have:

Severe abdominal pain or tenderness
Persistent vomiting (more than 3 times in 24 hours)
Bleeding from gums, nose or in urine/stools
Sudden drop in temperature (below 38°C) after days of high fever
Feeling cold, clammy or confused (shock)