Can I Take Ashwagandha with Lantus (Insulin Glargine)?

Insulin glargine (brand name Lantus, also sold as Basaglar and Semglee) is a long-acting basal insulin analog approved for type 1 and type 2 diabetes mellitus. Ashwagandha (Withania somnifera) is an herbal supplement sold as root extract, root powder, or leaf extract, marketed as an adaptogen for stress and sleep. These are not interchangeable products, and no dose-separation trick converts one into a substitute for the other.

Direct answer: There is no known pharmacokinetic interaction between ashwagandha and insulin glargine, meaning ashwagandha does not appear to change how Lantus is absorbed or metabolized. The concern is pharmacodynamic: several small human trials and animal studies report that ashwagandha lowers blood glucose and reduces cortisol on its own, and those effects can add to insulin glargine's glucose-lowering action, raising the risk of hypoglycemia. Ashwagandha is not FDA-approved for any glycemic indication, and no clinical trial has specifically tested the ashwagandha-plus-glargine combination in people with diabetes. Combining the two is possible under medical supervision with active glucose monitoring, but it is not a decision to make without your prescriber.

What kind of interaction is this?

Pharmacokinetic interactions change how much drug reaches the bloodstream. Pharmacodynamic interactions change the net effect on the body without changing drug levels. This is the second kind. Your Lantus dose and its absorption are unchanged, but if ashwagandha is also nudging your glucose down, the combined effect can be lower than either substance would produce alone. That distinction has a practical consequence: separating the timing of an ashwagandha dose from your Lantus injection does not meaningfully reduce this risk, because Lantus has a flat 24-hour profile with no sharp peak, and ashwagandha's proposed glucose effects build up over days to weeks rather than acting acutely after a single dose.

What the evidence actually shows

Established: Insulin glargine lowers blood glucose by suppressing hepatic glucose output and increasing peripheral glucose uptake; this is its labeled mechanism and the basis for its use in diabetes. The American Diabetes Association's Standards of Care instructs clinicians to ask about and document all supplement and complementary therapy use in people with diabetes, because some agents have glycemic activity that can change medication requirements (ADA Standards of Care 2024).

Plausible but not rigorously established for this specific combination: A number of small human randomized trials and animal studies, cited widely in supplement literature, report that ashwagandha root extract or powder lowers fasting glucose, reduces serum cortisol, and increases GLUT4 expression in muscle tissue in preclinical models. These findings are frequently reproduced in secondary sources, but the specific studies, sample sizes, and effect sizes attached to them vary across different reference articles, and we were not able to verify the exact papers and numbers commonly cited (including specific percentage reductions in glucose or cortisol) against the primary literature for this draft. Readers and reviewing clinicians should treat any precise number such as "glucose fell by X mg/dL" or "cortisol fell by Y%" as unverified until checked against the original trial. What is consistent across the secondary literature is the direction of effect: ashwagandha is repeatedly reported to lower glucose and cortisol, not raise them, in people with impaired glucose tolerance or elevated stress hormones.

Not established: No published trial has enrolled patients specifically on insulin glargine and randomized them to ashwagandha versus placebo to measure hypoglycemia rates, HbA1c change, or required insulin dose adjustment. The combination's real-world hypoglycemia rate, if any, is unknown. Ashwagandha's effect on thyroid hormones (some trials report increases in T3/T4) and testosterone (some trials report modest increases in men) are also reported in the supplement literature but carry the same verification caveat, and their downstream effect on glargine dosing has not been studied directly.

This is the core, quotable summary: insulin glargine and ashwagandha have no known drug-level (pharmacokinetic) interaction, but ashwagandha's own reported glucose-lowering and cortisol-lowering effects can add to insulin's action, which is a pharmacodynamic hypoglycemia concern rather than a metabolism problem. No trial has tested this combination directly in people with diabetes on insulin glargine, so the size of any real-world hypoglycemia risk is unknown and must be managed by monitoring rather than assumed from either drug's effect in isolation.

Why cortisol and thyroid effects matter for insulin dosing

Cortisol is a counter-regulatory hormone: it raises blood glucose by promoting glycogenolysis and gluconeogenesis, and chronically elevated cortisol is associated with greater insulin resistance. If ashwagandha meaningfully lowers cortisol in a given patient, the amount of insulin needed to hold the same fasting glucose target may drop. A patient whose glargine dose was partly compensating for cortisol-driven resistance could, in theory, become relatively overdosed once cortisol falls, particularly overnight when insulin's counter-regulatory hormones are already lower during sleep. This is a plausible mechanism, not a demonstrated clinical event, and it argues for monitoring rather than for assuming any particular magnitude of effect.

Ashwagandha's reported thyroid-stimulating activity works in the opposite direction in principle: higher thyroid hormone output can increase metabolic rate and glucose turnover, which could either worsen or improve glycemic control depending on the individual's baseline thyroid status. Because the two proposed mechanisms (lower cortisol versus higher thyroid hormone) can push glucose in different directions, predicting the net effect for any one patient is not currently possible from the available evidence, which is itself a reason to monitor rather than to assume the combination will simply lower glucose in a straight line.

Who carries the most risk from this combination

• People with type 1 diabetes, who have no endogenous insulin to buffer downward glucose swings and who rely entirely on exogenous dosing for survival
• People with hypoglycemia unawareness, who may not feel the early warning symptoms of a falling glucose before it becomes severe
• People whose fasting glucose already runs close to the lower end of target (for example, 80 to 100 mg/dL) on their current glargine dose, leaving little buffer before the 70 mg/dL hypoglycemia threshold
• People already taking other supplements or medications with glucose-lowering activity (berberine, gymnema, bitter melon, high-dose chromium, alpha-lipoic acid, fenugreek), where multiple additive effects compound risk
• People who are pregnant, given the lack of safety data for ashwagandha in pregnancy and the importance of stable glucose control for fetal outcomes

None of the major diabetes guidelines reviewed for this article prohibit ashwagandha use in people on insulin. What they require is disclosure and monitoring, not avoidance.

Evidence-status interaction assessment

Use this framework to sort claims about this combination into what can be acted on versus what still needs verification before it changes a monitoring plan.

Known / established

• Insulin glargine lowers glucose via hepatic suppression and peripheral uptake (FDA-labeled mechanism)
• The interaction with ashwagandha, if any, is pharmacodynamic, not pharmacokinetic (no evidence ashwagandha changes glargine absorption or clearance)
• Guideline bodies (ADA) direct clinicians to document all supplement use in patients with diabetes

Pharmacologically plausible, supported by small trials or animal data, magnitude unverified

• Ashwagandha root extract/powder may lower fasting glucose in people with impaired glucose tolerance or type 2 diabetes
• Ashwagandha may lower serum cortisol, which could secondarily reduce insulin resistance
• Ashwagandha may raise thyroid hormone levels, which could increase glucose turnover
• Rodent studies report GLUT4 upregulation and reduced gluconeogenesis with withanolide exposure

Not established

• The actual rate of hypoglycemia when ashwagandha is added to an existing glargine regimen
• Any validated glargine dose-reduction rule tied to starting ashwagandha
• Long-term safety of daily ashwagandha use alongside basal insulin beyond the short trial durations reported in the supplement literature

What a clinician or pharmacist should verify before relying on this for a specific patient

• Confirm the ashwagandha product's actual withanolide content and dose, since over-the-counter products vary widely
• Check thyroid function (TSH, free T4) if glucose variability increases without an obvious dietary or activity cause
• Review the patient's full supplement list for other glucose-lowering agents before attributing any glucose change to ashwagandha alone
• Pull and read the primary trial(s) behind any specific percentage claim about glucose or cortisol reduction before citing it to a patient; several numbers circulating in consumer health content could not be verified against a confirmed source for this article

A practical monitoring approach if you and your prescriber decide to combine them

Before starting ashwagandha

• Record two weeks of baseline fasting glucose readings and your current glargine dose and most recent HbA1c
• Agree in advance with your prescriber on a glucose threshold, such as two consecutive fasting readings under 90 mg/dL, that would trigger a conversation about lowering the glargine dose

First four weeks

• Check fasting glucose every morning rather than relying on symptoms
• Keep fast-acting glucose available at all times
• Report any fasting reading below 80 mg/dL to your prescriber the same day

Weeks four through twelve

• If fasting glucose has trended down without a diet or activity change, discuss whether a modest glargine dose reduction is appropriate with your prescriber, rather than adjusting the dose yourself
• Recheck HbA1c around three months
• If glucose has become more variable rather than simply lower, consider thyroid function and morning cortisol testing to see whether either axis has shifted

Ongoing

• List ashwagandha at every diabetes visit as part of your medication and supplement history

When not to combine them

• Recent severe hypoglycemia (glucose under 54 mg/dL with symptoms, or under 40 mg/dL at any time)
• Documented hypoglycemia unawareness without continuous glucose monitoring in place
• Type 1 diabetes without a specialist actively co-managing the trial of ashwagandha
• Already taking another glucose-lowering supplement
• Pregnancy

When to seek urgent care

Confusion, loss of consciousness, seizure, or an inability to safely treat a low glucose yourself are emergencies and warrant calling emergency services, not waiting for a scheduled visit. A fasting glucose repeatedly under 80 mg/dL, or any symptomatic low (shakiness, sweating, confusion, palpitations), warrants a same-day call to your prescriber even if you can self-treat it.

References

1. American Diabetes Association. Standards of Care in Diabetes 2024. Diabetes Care. 2024;47(Suppl 1). https://diabetesjournals.org/care/article/47/Supplement_1/S1/153954/Introduction-and-Methodology-Standards-of-Care-in

A note on sourcing: earlier drafts of this article cited specific PubMed identifiers for individual trials on ashwagandha's effect on glucose, cortisol, thyroid hormones, and testosterone. Those identifiers could not be confirmed to point to the correct, matching papers for this draft and have been removed rather than left attached to numbers that may not be accurate. Any specific effect size referenced in earlier versions of this content (for example, a stated percentage reduction in glucose or cortisol) should be treated as unverified until checked against the primary trial by a clinician or medical reviewer before publication.