Astragalus is generally well tolerated, but several groups of people should avoid it or use it only under medical supervision. The biggest concern is its immune-boosting activity, which can be harmful if your immune system is already overactive or if you take medications that deliberately suppress it. People with autoimmune diseases, those on immunosuppressants, individuals taking lithium or blood pressure medication, and pregnant or breastfeeding women all fall into higher-risk categories.
People With Autoimmune Diseases
Astragalus stimulates immune activity, which is the opposite of what you want when your immune system is already attacking your own tissues. The National Center for Complementary and Integrative Health states directly that people with autoimmune diseases should avoid astragalus because it might worsen symptoms. This applies to conditions like lupus, rheumatoid arthritis, multiple sclerosis, type 1 diabetes, Crohn’s disease, and psoriasis.
The core problem is that astragalus ramps up certain immune cells and signaling pathways. In a healthy person, that can support infection defense. In someone with an autoimmune condition, it can intensify the misdirected immune response that’s causing damage in the first place. Even if your autoimmune disease feels well controlled, adding an immune stimulant introduces an unpredictable variable.
People Taking Immunosuppressant Drugs
If you take medications designed to suppress your immune system, astragalus can work against them. Specifically, it may reduce the effectiveness of drugs like tacrolimus and cyclosporine, which are commonly prescribed after organ transplants and for severe autoimmune conditions. These medications require careful blood-level management, and anything that counteracts their effect can lead to organ rejection or disease flares.
This interaction extends broadly to the immunosuppressant drug class. If you’re on any medication intended to dial down immune function, whether for a transplant, autoimmune disease, or another condition, astragalus poses a real risk of undermining your treatment.
People Taking Lithium
Astragalus may slow the rate at which your body clears lithium, a medication used primarily for bipolar disorder. When lithium builds up in the blood, it can reach toxic levels, causing symptoms that range from tremors and nausea to confusion, seizures, and kidney damage. Lithium already has a narrow therapeutic window, meaning the difference between an effective dose and a dangerous one is small. Adding a supplement that further reduces lithium excretion raises the risk of tipping into toxicity.
If you take lithium, this is one of the more serious astragalus interactions to be aware of, because the consequences of elevated lithium levels can be severe and sometimes irreversible.
People on Blood Pressure Medication
Astragalus can lower both systolic and diastolic blood pressure on its own. If you already take antihypertensive medication, combining the two may drop your blood pressure to unhealthy levels. Memorial Sloan Kettering Cancer Center notes that the combination may have additive effects, though the exact clinical significance isn’t fully established.
Signs that your blood pressure has dropped too low include dizziness, lightheadedness, fainting, blurred vision, and fatigue. In one study, participants taking astragalus experienced fatigue, headache, and low blood pressure as side effects, though these resolved within 24 hours. If you’re already managing low blood pressure or are sensitive to blood pressure changes, astragalus adds unnecessary risk.
People Taking Diabetes Medications
Astragalus has demonstrated blood sugar-lowering effects in research. Animal studies show it improves insulin sensitivity in skeletal muscle, allowing cells to respond more effectively to insulin and pull glucose from the bloodstream. That’s a useful property on its own, but if you’re already taking medications that lower blood sugar, the combined effect could push your levels too low.
Hypoglycemia, or abnormally low blood sugar, causes shakiness, sweating, confusion, irritability, and in severe cases, loss of consciousness. If you manage diabetes with insulin or oral medications, adding astragalus without adjusting your treatment could create unpredictable dips in blood sugar that are difficult to anticipate.
Pregnant or Breastfeeding Women
There isn’t enough safety data on astragalus use during pregnancy or breastfeeding to consider it safe. Most health authorities recommend avoiding it during these periods as a precaution. The immune-modulating effects alone raise concerns about how the supplement might affect fetal development or a newborn receiving breast milk. Without human studies confirming safety, the cautious approach is to skip it entirely until after breastfeeding ends.
People With Legume Allergies
Astragalus belongs to the Fabaceae family, the same plant family as peanuts, soybeans, chickpeas, and lentils. If you have a known allergy to legumes, there’s a possibility of cross-reactivity with astragalus. Allergic reactions could range from mild skin irritation to more serious responses depending on your sensitivity. This doesn’t mean everyone with a peanut allergy will react to astragalus, but the shared plant family is worth noting if you have a history of legume-related allergic reactions.
People With Advanced Kidney Disease
Research on astragalus and kidney health has only been conducted in people with mild to moderate chronic kidney disease (stages 2 and 3), where no severe adverse reactions were recorded. However, researchers explicitly noted that results cannot be applied to patients with stage 4 or stage 5 kidney disease. Because astragalus affects how the body processes and excretes certain substances (as seen with lithium), people with significantly reduced kidney function face unknown risks. The kidneys’ diminished ability to filter and clear compounds makes any supplement with active biological effects a potential concern.