Minoxidil is one of the most popular treatments available for hair loss. While it has proven effective for many, it’s important to be aware of its potential side effects so you can use it safely.

Here we’ll look at topical and oral minoxidil’s most commonly reported side effects. Though oral minoxidil is less widely used for hair loss, it’s still important to be aware of its distinct effects. Additionally, we’ll provide tips to help you minimize these side effects when possible.

What is minoxidil, and how is it used?

Minoxidil is a medication that was first made to help treat high blood pressure, but doctors and scientists discovered it had a surprising side effect. Patients using it experienced hair growth. Now, it is more well-known for this use than for its original purpose.¹ 

Topical minoxidil has become a first-line treatment for a condition called androgenetic alopecia.² This is a common type of hair loss that usually affects the top and front of your head. Healthcare providers also occasionally use it off-label to treat other types of hair loss disorders.³

Researchers think that minoxidil affects hair follicles by enhancing hair growth and reducing hair loss.⁴ 

It takes time to see results when starting minoxidil. You may begin to notice changes after about eight weeks, but results usually occur after about four months.⁵ So, it’s important to be consistent and patient. If you stop using it too soon, you might not see how well it can work for you.

What are the side effects of topical minoxidil? 

Topical minoxidil solution is generally recognized as a safe treatment for hair loss.⁶ However, like any medication, it can have side effects, though they are usually mild. If you do experience adverse effects from using minoxidil on your scalp, they are typically limited to the area where you applied the medicine and don’t affect other areas.⁷

The most frequent side effect of topical minoxidil is irritant contact dermatitis.⁸ This is a kind of skin irritation that can happen where you apply the medication. Symptoms include itching and scaling of the scalp, which can be uncomfortable but are not usually serious.⁹ If you have irritation that persists or worsens, it’s a good idea to talk to your healthcare provider.

Some people might be allergic to topical minoxidil or an ingredient in the formula like propylene glycol (PG).¹⁰ Allergic reactions are not very common, but they can happen. If you are allergic or sensitive to PG, your medical provider can order a PG-free formula.¹¹ If you think you might be having an allergic reaction to minoxidil, stop using it and get medical attention right away.

Interestingly, a common but temporary side effect of minoxidil is hair shedding.¹² That might seem worrying, especially since you use the medication to improve hair growth. But, this is a known potential side effect!¹³ When you first start using it, it can cause old hairs to fall out as it stimulates new hair growth. This shedding usually stops after a few weeks as your hair cycle adjusts to the treatment.¹⁴

As with any medication, it’s always a good idea to use minoxidil exactly as directed and to talk to your healthcare provider if you have any concerns or experience adverse effects. They can guide you on managing side effects or adjusting your treatment if necessary.

What are the side effects of oral minoxidil? 

Oral minoxidil isn’t typically used for hair loss, but it is occasionally prescribed off-label, especially when topical treatments are ineffective.¹⁵ It’s important to be aware that oral minoxidil can have more serious side effects than its topical counterpart, which is why its use for hair loss is less common.¹⁶ 

One of the most significant risks associated with oral minoxidil is hypotension or low blood pressure.¹⁷ This can be a serious issue, especially for those who already have low blood pressure or other cardiovascular conditions. The medication can also cause sodium and fluid retention, leading to weight gain.¹⁸ In more severe cases, this retention can contribute to congestive heart failure, a condition where the heart struggles to pump blood effectively.¹⁹

Other adverse effects you might experience include headaches that feel like a pulsating sensation, itchy eyes, and skin rashes, including bullous eruptions (large blisters).²⁰ Some women may also experience polymenorrhea, a condition where menstrual cycles occur more frequently than usual.²¹

Hypertrichosis, or excessive hair growth, is another possible side effect.²² This can occur in areas other than the scalp, which might be undesirable. On very rare occasions, oral minoxidil was reported to cause blood disorders such as thrombocytopenia (low platelet count) and leukopenia (low white blood cell count), which can affect the body’s ability to clot blood and fight infection, respectively.²³ Nausea, vomiting, and changes in your electrocardiogram (ECG), which measures heart rhythm, are also potential side effects.²⁴

Given these risks, oral minoxidil should be used cautiously and under close supervision by a healthcare provider. If you’re considering oral minoxidil for hair loss, it’s crucial to discuss these potential side effects with your medical provider to determine if it’s suitable for you.

How can you minimize minoxidil side effects? 

Not all side effects of minoxidil can be prevented, but there are some strategies that you can use to minimize them potentially.

First, always apply minoxidil exactly as directed, either by the instructions on the packaging or as advised by your medical provider. Using your topical minoxidil solution more than recommended won’t increase its effectiveness and may lead to systemic absorption.²⁵ This can increase the risk of hair growth in unwanted areas, an issue particularly relevant if you’re using it for hair loss.²⁶

If you’re allergic or sensitive to propylene glycol, a common ingredient in minoxidil formulations, your healthcare provider can likely order a PG-free formula. This alternative formulation can reduce the likelihood of allergic reactions or skin irritation.²⁷ 

If you’re using other topical treatments in the same area where you apply minoxidil, it’s important to talk to your healthcare provider. Your provider can advise you how to safely use minoxidil alongside other topical treatments.

How Curology can help 

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You don’t need a prescription for certain strengths of topical minoxidil, but if you want to target your hair loss effectively with a custom formula, we’re here to help. Talk to your Curology provider to see if our Hair Formulaᴿˣ is right for you, and if it is, they’ll prescribe your treatment with active ingredients to support your hair growth goals. 

P.S. We did the homework, so you don’t have to: 

1. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. (August 2019).

2. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid.

3. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid.

4. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid.

5. Patel, P., et al. Minoxidil. StatPearls. (2023, November 15).

6. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid.

7. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid.

8. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid.

9. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid.

10. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid.

11. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid.

12. Patel, P., et al. Minoxidil. StatPearls. Ibid.

13. Patel, P., et al. Minoxidil. StatPearls. Ibid.

14. Patel, P., et al. Minoxidil. StatPearls. Ibid.

15. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid.

16. Patel, P., et al. Minoxidil. StatPearls. Ibid.

17. Patel, P., et al. Minoxidil. StatPearls. Ibid.

18. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid.

19. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid.

20. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid.

21. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid.

22. Pfizer. Loniten® minoxidil tablets, USP. (January 2015).

23.  Pfizer. Loniten® minoxidil tablets, USP. Ibid.

24.  Pfizer. Loniten® minoxidil tablets, USP. Ibid.

25. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid

26. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid.

27. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid.

28. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid.

29. Müller Ramos, P., et al. Female-pattern hair loss: therapeutic update. Anais Brasileiros de Dermatologia. (July-August 2023).

30. Müller Ramos, P., et al. Female-pattern hair loss: therapeutic update. Anais Brasileiros de Dermatologia. Ibid.

31. Müller Ramos, P., et al. Female-pattern hair loss: therapeutic update. Anais Brasileiros de Dermatologia. Ibid.

32. Müller Ramos, P., et al. Female-pattern hair loss: therapeutic update. Anais Brasileiros de Dermatologia. Ibid.

33. Müller Ramos, P., et al. Female-pattern hair loss: therapeutic update. Anais Brasileiros de Dermatologia. Ibid.

34. Patel, P., et al. Minoxidil. StatPearls. Ibid.

35. Patel, P., et al. Minoxidil. StatPearls. Ibid.

36. Patel, P., et al. Minoxidil. StatPearls. Ibid.

37. Patel, P., et al. Minoxidil. StatPearls. Ibid.

38.  Nestor, M. S., et al. Treatment options for androgenetic alopecia: Efficacy, side effects, compliance, financial considerations, and ethics. Journal of Cosmetic Dermatology. (December 2021).

39. Patel, P., et al. Minoxidil. StatPearls. Ibid.

40. Nestor, M. S., et al. Treatment options for androgenetic alopecia: Efficacy, side effects, compliance, financial considerations, and ethics. Journal of Cosmetic Dermatology. Ibid.

41. Nestor, M. S., et al. Treatment options for androgenetic alopecia: Efficacy, side effects, compliance, financial considerations, and ethics. Journal of Cosmetic Dermatology. Ibid.

42. Nestor, M. S., et al. Treatment options for androgenetic alopecia: Efficacy, side effects, compliance, financial considerations, and ethics. Journal of Cosmetic Dermatology. Ibid.

43. Nestor, M. S., et al. Treatment options for androgenetic alopecia: Efficacy, side effects, compliance, financial considerations, and ethics. Journal of Cosmetic Dermatology. Ibid.

44. Nestor, M. S., et al. Treatment options for androgenetic alopecia: Efficacy, side effects, compliance, financial considerations, and ethics. Journal of Cosmetic Dermatology. Ibid.

45. Suchonwanit, P., et al. Minoxidil and its use in hair disorders: a review. Drug design, development and therapy. Ibid.

Jessica Lee is a certified Nurse Practitioner at Curology. She received her Master in Nursing from Samuel Merritt University in Oakland, CA.

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Written by

Curology Team

Medically reviewed by

Jessica Mefford, NP