Finding the right tests…
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Finding the right tests…
Serology
DENGUE IgM checks your blood for one specific antibody your immune system makes in response to a recent dengue infection. Unlike the NS1 test, which looks for the virus itself, IgM only shows up once your body has had a few days to react — usually from day 4 or 5 of illness — so this test works best once the earliest days of fever have passed. Once it appears, IgM generally stays detectable for around three months, marking the infection as recent rather than pinpointing the exact day it started. If you're tested in the first three days of fever, your doctor may combine this with NS1, since a negative IgM that early doesn't rule dengue out.
A dengue IgM result comes back as a positive or negative reading, showing whether this specific antibody has appeared in your blood yet. IgM typically becomes detectable from day 4 or 5 of illness and can be picked up for roughly the next twelve weeks, so it's most reliable from about day 5 onward rather than on the first day of fever. Because a single sample can't reliably tell a first-time infection from a repeat one, your doctor may look at it alongside NS1 or an IgG result. A single blood sample is enough, with no fasting needed.
IgM is the first type of antibody your immune system produces against a new infection, and with dengue it typically becomes detectable around four to five days after symptoms start — later than the NS1 antigen, but earlier than IgG in someone who's never had dengue before.
A positive IgM taken after day 5 of illness is read as a presumptive recent dengue infection. Tested any earlier than that, a negative result doesn't rule dengue out, since IgM may simply not have risen yet — this is why doctors often test NS1 or repeat testing rather than relying on IgM alone in the first days of fever.
Once positive, dengue IgM generally stays detectable for around three months after infection, and sometimes longer, so a positive result confirms a dengue infection happened recently without pinning down the exact day. In someone who has had dengue before, IgM can rise more slowly or less strongly, and IgG becomes the dominant signal instead, which is one reason your doctor may test both together rather than IgM in isolation.
IgM generally becomes detectable from around day 4 or 5 of illness, based on CDC guidance, so testing in the first few days of fever can miss it even in a genuine infection.
If you're tested very early in your illness, your immune system may not have made enough IgM yet for the test to pick up. Your doctor may repeat the test later or check NS1 instead.
It generally stays detectable for around three months after infection, and sometimes longer, so a positive result confirms the infection was recent without pinpointing the exact day it started.
NS1 detects a piece of the virus itself and shows up earlier, in the first week of illness, while IgM is an antibody your immune system makes in response and typically appears a few days later.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
A positive IgM taken after day 5 of illness is read as a presumptive recent dengue infection. Your doctor will weigh it alongside your symptoms and other test results.
Your doctor may add one, since comparing IgM and IgG together can help show whether this is your first dengue infection or a repeat one, which affects how closely you're monitored.
No. No special preparation, including fasting, is needed before this blood draw.