Ashwagandha can affect several types of blood tests, both by genuinely changing what’s happening in your body and by causing false readings on certain lab equipment. If you’re taking ashwagandha and have bloodwork coming up, the most important areas to be aware of are thyroid panels, hormone levels, blood sugar markers, and one specific test for the heart medication digoxin.
Thyroid Panel Results
This is the blood test most clearly affected by ashwagandha. The supplement appears to stimulate the thyroid gland to produce more thyroxine (T4), the main circulating thyroid hormone. In animal studies, ashwagandha increased T4 levels by roughly 111%. These aren’t false readings on lab equipment. Ashwagandha is genuinely shifting your thyroid hormone levels.
In one documented case, a 73-year-old woman who had been taking ashwagandha for two years to self-treat her hypothyroidism arrived at the hospital with a dangerously suppressed TSH level of less than 0.01 (normal range is 0.27 to 4.20), along with symptoms of thyrotoxicosis: tremor, rapid heartbeat, dizziness, and hair thinning. After she stopped taking ashwagandha, her TSH returned to normal within two weeks and eventually climbed back to a level consistent with her underlying hypothyroid condition.
Some commercially available ashwagandha supplements have also been found to contain actual thyroid hormones (T3 and T4) in amounts that exceed therapeutic doses used to treat hypothyroidism. So if your thyroid panel comes back abnormal and you’re taking ashwagandha, the supplement is a strong suspect. This is especially important if you’re already on thyroid medication, since ashwagandha could make your dosage appear too high or too low depending on timing.
Digoxin Levels Can Read Falsely
If you take the heart medication digoxin, ashwagandha can directly interfere with the lab equipment used to measure your drug levels. This is a different problem from changing what’s actually in your blood. Components in ashwagandha cross-react with certain immunoassays, the tests labs use to measure how much digoxin is in your serum.
One type of test (fluorescence polarization immunoassay) produces falsely high digoxin readings when ashwagandha is present, while another type (microparticle enzyme immunoassay) produces falsely low readings. Both directions are dangerous: a falsely high reading might lead your doctor to reduce a dose you actually need, while a falsely low reading could lead to a dose increase you don’t need. If you take digoxin and use ashwagandha, your prescriber needs to know.
Testosterone, DHEA-S, and Cortisol
Ashwagandha produces real changes in reproductive and stress hormone levels. In a randomized, placebo-controlled crossover study of overweight men, eight weeks of supplementation raised testosterone by about 14.7% and DHEA-S (a precursor hormone made by the adrenal glands) by about 18% compared to placebo. Both differences were statistically significant.
Cortisol, the stress hormone people most associate with ashwagandha, showed a more modest picture in controlled research. The same study found cortisol levels were 7.8% lower during ashwagandha use, but this difference did not reach statistical significance. So while ashwagandha may nudge cortisol downward, the testosterone and DHEA-S shifts are more likely to show up on your bloodwork in a meaningful way.
Blood Sugar and HbA1c
Ashwagandha can lower fasting blood glucose and HbA1c, the marker that reflects your average blood sugar over the past two to three months. In clinical research, fasting blood sugar dropped from 97.2 to 91.9 mg/dL in one intervention group, while HbA1c decreased by about 0.2 percentage points (from 5.8% to 5.6%). A separate analysis found a mean HbA1c reduction of 0.25%.
These shifts are modest but not trivial. A 0.2% change in HbA1c could be the difference between a result that looks prediabetic and one that looks normal, or it could make a diabetic patient’s glucose control appear better managed than it would be without the supplement. If your doctor is tracking your blood sugar trends over time, the supplement adds a variable that could obscure the real picture.
Liver Enzymes
In controlled clinical trials, ashwagandha has not caused elevations in liver enzymes like ALT, AST, or alkaline phosphatase. A 32-week placebo-controlled trial in osteoarthritis patients found no changes in any liver markers. So for most people, a standard liver panel won’t look different because of ashwagandha.
However, ashwagandha has been linked to rare cases of clinically apparent liver injury, first reported in 2017, with an increasing number of cases since. The liver injury typically appears 2 to 12 weeks after starting the supplement and usually presents with jaundice and itching. Most cases resolve completely after stopping the supplement, but rare fatal outcomes and emergency liver transplants have been reported, particularly in people with preexisting liver disease. The National Institutes of Health gives ashwagandha a likelihood score of “B,” meaning it’s a likely cause of clinically apparent liver injury. If your liver enzymes come back elevated and you’re taking ashwagandha, it’s worth flagging for your doctor even though this outcome is uncommon.
Blood Clotting Tests
Withaferin A, one of the active compounds in ashwagandha, has anticoagulant and antiplatelet properties. In laboratory and animal studies, it prolonged both prothrombin time (PT) and activated partial thromboplastin time (aPTT), inhibited platelet aggregation, and increased bleeding time. It also interfered with fibrin polymerization, the process that forms the structural backbone of blood clots.
This matters most if you’re on blood-thinning medications and your doctor monitors your clotting times. Ashwagandha could push your INR or PT results higher than they would otherwise be, potentially making your anticoagulant therapy harder to manage safely.
Kidney Function and Lipids
Kidney markers appear largely unaffected. A 24-week randomized, double-blind, placebo-controlled study found no clinically significant differences between ashwagandha and placebo groups for creatinine, urea, or blood urea nitrogen. Creatinine averaged 0.79 mg/dL in the ashwagandha group versus 0.75 in placebo, a gap that was neither statistically nor clinically meaningful.
For cholesterol and triglycerides, animal research shows ashwagandha can reduce total cholesterol, triglycerides, and VLDL while raising HDL. The supplement appears to influence lipid metabolism by affecting how fat cells develop and how mitochondria burn energy. Whether these effects translate to noticeable changes on a human lipid panel at typical supplement doses is less certain, but if you see modest improvements in your cholesterol numbers after starting ashwagandha, the supplement could be contributing.
What to Tell Your Doctor
The simplest step is to list ashwagandha on your intake forms alongside any medications. Many clinicians don’t ask about supplements specifically, and the interactions above are not widely known outside of pharmacology. Thyroid panels, digoxin monitoring, clotting tests, and hormone panels are the blood tests most likely to be affected in ways that could change a clinical decision. For routine metabolic panels covering kidney and liver function, ashwagandha is unlikely to cause abnormal results in otherwise healthy people, though the rare liver injury risk is real enough to keep in mind.