Most people with sickle cell disease find out at birth through routine newborn screening, which has been standard across all 50 U.S. states for decades. If you weren’t screened as a newborn, or you’re wondering whether symptoms you’re experiencing could point to sickle cell, a simple blood test can give you a definitive answer. Here’s what to look for and how testing works.
Newborn Screening Catches Most Cases
Between 12 and 48 hours after birth, a healthcare provider takes a small blood sample from the baby’s heel and sends it to a state laboratory. This blood spot test screens for sickle cell disease along with dozens of other conditions. If the result comes back positive, a state coordinator contacts the baby’s pediatrician with next steps, and confirmatory testing follows.
Because of universal screening, most people born in the U.S. after the mid-1980s already know their status. But if you were born outside the U.S., born before screening became standard in your state, or your records were lost, you may genuinely not know whether you carry sickle cell disease or the sickle cell trait.
Symptoms That Appear in Infants and Children
Babies with sickle cell disease typically don’t show symptoms until around 5 or 6 months old. That’s when the protective fetal hemoglobin they were born with begins to drop and the abnormal sickle hemoglobin takes over. The first sign is usually painful swelling in the hands and feet, often accompanied by fever. This happens when sickle-shaped red blood cells get stuck in tiny blood vessels and block blood flow to the small bones.
Other early signs in infants and toddlers include:
- Jaundice: a yellowish tint to the skin or whites of the eyes, caused by red blood cells breaking down faster than normal
- Extreme tiredness or fussiness: from anemia, since the body isn’t getting enough oxygen from its depleted supply of healthy red blood cells
- Pale skin or lips: another sign of anemia
Pain episodes can begin in children as young as 1 year old. These happen when sickle cells clump together and block blood flow, cutting off oxygen to tissues. The pain can strike the chest, abdomen, joints, or bones and may last hours to days.
Signs in Older Children and Adults
If sickle cell disease goes undiagnosed, it tends to make itself known through recurring, hard-to-explain symptoms. Chronic fatigue is common because sickle cells die much faster than normal red blood cells, leaving the body perpetually short on oxygen-carrying capacity. Frequent infections are another hallmark, especially in children, because the spleen (which filters bacteria from the blood) gets damaged early by trapped sickle cells.
One dangerous complication to recognize is splenic sequestration, where sickle cells suddenly pile up in the spleen, causing it to swell rapidly. This shows up as pain on the left side of the abdomen along with sudden weakness, pale lips, fast breathing, and a racing heartbeat. It happens most often in children and requires immediate medical attention.
Adults who carry sickle cell disease without knowing it may have lived with milder forms of the condition, such as sickle cell SC disease or sickle beta-thalassemia, which can produce less severe symptoms for years before a crisis forces a diagnosis.
Sickle Cell Trait vs. Sickle Cell Disease
There’s an important difference between having sickle cell disease and carrying the sickle cell trait. You inherit one copy of the sickle hemoglobin gene from each parent. If you get two copies of the abnormal gene, you have sickle cell disease. If you get one normal copy and one sickle copy, you have sickle cell trait.
People with sickle cell trait typically have no symptoms. Their sickle hemoglobin levels stay below about 35% of total hemoglobin, with normal hemoglobin making up the rest. They can, however, pass the gene to their children. If both parents carry the trait, each pregnancy has a 25% chance of producing a child with sickle cell disease. That’s why knowing your trait status matters even if you feel perfectly healthy.
How Testing Works
The definitive test is called hemoglobin electrophoresis. It separates different types of hemoglobin in your blood and measures what percentage of each type you have. In a person without sickle cell, 95% to 98% of their hemoglobin is normal adult hemoglobin (HbA), with no sickle hemoglobin (HbS) present. A person with sickle cell disease will have a high percentage of HbS and little to no HbA. A person with the trait will have a mix of both.
There is a quicker screening option called the sickle solubility test, which detects the presence of sickle hemoglobin in a blood sample. It’s fast and accessible, but it has a major limitation: it can tell you whether sickle hemoglobin is present, but it can’t tell you how much is there. That means it can’t distinguish between sickle cell trait and sickle cell disease. Anyone who tests positive on a solubility test still needs hemoglobin electrophoresis to confirm the actual diagnosis.
If you’re an adult who has never been tested, any primary care provider can order hemoglobin electrophoresis. It’s a standard blood draw with results typically available within a few days.
Testing During Pregnancy
If both parents carry the sickle cell trait, prenatal testing can determine whether the baby will have sickle cell disease. Chorionic villus sampling can be done between 10 and 13 weeks of pregnancy, while amniocentesis is performed between 15 and 20 weeks. Both procedures collect a small sample of fetal genetic material that can be tested for the specific gene mutation that causes sickle cell, a single amino acid change in the hemoglobin gene where valine replaces glutamic acid.
Carrier screening for both parents is simpler and can happen before or during pregnancy with a basic blood test. Genetic counselors can walk you through the math of inheritance risk and help you understand what results mean for your family.
Ongoing Monitoring After Diagnosis
Knowing you have sickle cell disease is just the starting point. Children with sickle cell anemia are recommended to receive annual ultrasound screenings of the blood vessels in the brain from ages 2 to 16. These screenings measure blood flow speed and identify children at higher risk for stroke, one of the most serious complications of the disease. Children flagged as high-risk can start preventive treatment before a stroke ever happens.
Regular blood work tracks hemoglobin levels, organ function, and signs of complications like elevated bilirubin (a marker of red blood cell breakdown). Over time, sickle cell disease can affect the kidneys, lungs, eyes, and bones, so ongoing monitoring helps catch problems early when they’re more manageable.